Sunyata is the truth and compassion is not an illusion?

I have asked a similar question previously albeit, from Mahayana's point of view. See the link below. Some of the responses provided there may point you in the right direction.

If no sentient being exists, for whom is there compassion? 'A Guide to the Bodhisattva Way of Life' by Santideva

[Qualm:] If no sentient being exists, for whom is there compassion?

[Madhyamika:] For one who is imagined through delusion, which is accepted for the sake of the task.

[Qualm:] If there is no sentient being, whose is the task?

[Madhyamika:] True. The effort, too, is due to delusion. Nevertheless, in order to alleviate suffering, delusion with regard to one's task is not averted

A Guide to the Bodhisattva Way of Life' by Santideva, Chapter IX: The Perfection of Wisdom.

I think that Buddhism talks about suffering and its cessation -- states of woe, and the liberations from or antidotes to those states. For example the three poisons: desire, aversions, and ignorance are all harmful in their own way.

The Brahmaviharas are said to be the answer to, the right way to behave in, all social circumstances.

Meeting someone who's suffering, for example, you might feel suffering yourself -- or you might feel pity, superiority, aversion -- none of which are ideal. Whereas compassion is the right (correct or noble) answer, for that situation.

For other circumstances there are different answers. Meeting someone who's noble (and not suffering), for example, there's mudita as a correct answer. Or meeting someone who's evil, equanimity.

They (the brahmaviharas) are all good, but they're situational, they're the right response to what arises.

I think that "emptiness" is similar, in the same category -- not superior to compassion, not meant to say that compassion is a lie or non-existent -- but a correct response to a certain situation's arising. And the situation for which emptiness is a correct response or antidote isn't especially a social situation (for which you have the brahmaviharas) -- I think that emptiness is especially useful as an antidote for (suffering resulting from) the arising of fixed or unwholesome views -- views of all sorts, "I'd like to be famous but I'm not", "I'm right and he's wrong", "I wish my friend were still alive", and so on and so on and so on.

One more thing, I think (because I read it, not because I've been taught it) that there's Tibetan (Mahayana) doctrine which says that even "Arhat" is a temporary state/place of rest on the longer journey towards becoming a Buddha. And if compassion is the primary (or only) motive of the Buddha, perhaps that's an argument that it shouldn't be seen as inferior to or erased by emptiness.

The Buddhist problematic — the central concern that Buddhism focuses on – is self-illusion. We believe that we should have a different relationship with the world than we do, a different relationship with others than we actually have, even a different relationship to ourselves. That self-illusion leads to discontentment and craving. Emotions aren't exactly illusions (or deceptive) in this sense. Emotions reflect karma: they are states that arise because we are caught by self-illusion.

Compassion is the state that arises when we see the world as it is, without self-illusion. When we understand how much of the world is a tangle of self-illusions, and how subtle and intractable those self-illusions can be, what other state could arise except compassion? Compassion isn't sympathy (an identification with someone else's self-illusion); it isn't judgement (a self-illusion that someone knows better or is better or should be better). Compassion arises when we recognize "here we are", and see the conditions laid before us.

You know that feeling when you look at the world and can't help but see that it is messed up (all wrong!)? And you feel a kind of aversion, a mix of pity and disgust?

Guess what, the enlightened folks looking at the world notice the same exact problems as you, except they don't feel aversion or disgust. Instead they feel compassion. So compassion is the purified equivalent of the same feeling as you have when looking at the world, just purified. Cool, huh? It can be purified but it never goes away.

Compassion is not yet another misleading feeling, because it's based on Knowledge and Truth, not on the Three Poisons. It is based on knowledge and truth of the illusion and the suffering that the confused sentient beings have to helplessly endure generation after generation. This is why Mahayana teaching states that compassion automatically and unconditionally arises in the mind of enlightened being, it cannot not arise.

Compassion is a form of Love, a form of being in harmony with reality. You see the way things work for sentient beings, you see they have to go through all these phases as part of growing up - and you are at peace with it, even though it involves considerable amount of growing pains and suffering. You love everything unconditionally, with all its imperfections, including even the very Samsara itself. Because you love it and accept it as it is, but at the same time you are acutely aware of how far it needs to grow yet, you feel compassion.

As for your comments about Shunyata, it exhibits even greater confusion on your part. You seem to think that The Good, The Kindness, the Peace is on the equal footing with The Bad, The Selfish, the Discord - vis-a-vis the transcendence that is Shunyata. This is wrong understanding. The worldly Good / The worldly Right is a crude approximation of The Ultimate Good/Right which is Shunyata. So it's not that we have to abandon The Good (including compassion) on our way to Shunyata, not at all. Rather, we have to perfect and refine our ethics, because the perfect Goodness (the Paramita level of transcendental goodness) is nothing else but Shunyata.

This is why all Buddhas of past, present, and future instruct sentient beings to adopt and perfect the Sila (ethics) not to abandon them. Abandoning compassion under an excuse of Shunyata is an evil path, not Buddha-Dharma.

The Good (including Compassion) is how the absolute of Shunyata gets projected onto the relative world of sentient beings. Compassion is a shadow of Prajna, in a manner of speaking.

There was an archaeological find at the site of the famed Buddhist university Nalanda. It was either on a piece of pottery or a mural inscription, I forget which, but the words in Sanskrit read "Seeing emptiness, he feels compassion".

You are laboring under a mistake. The reality is that compassion and emptiness are the same thing. When we directly perceive emptiness, we experience the compassion of the Buddha. It isn't a feeling or an emotion but rather an instinctual reaction to reality. Zen master Dogen likens it to a hand that reaches for a pillow in the night. The compassion generated by emptiness has no forethought or preconception. It simply happens. It simply is. The compassion of emptiness is a vastness that underlies us all.

You have put it wrongly. You say all my emotions are deceptive, that is an incorrect observation. Correct way to put it is emotions are not me , mine or myself. It will come as a surprise that you can also say consciousness is not me,mine or myself. Does that mean you will become devoid of consciousness? No you won’t. Does that mean consciousness is deceptive ? No.Similarly you do not become devoid of emotions (including compassion) and those emotions are not deceptive... you just don’t cling to it...Buddha was deeply compassionate... whatever he spoke he spoke out of compassion....Emotions are not deceptive...consciousness is not deceptive... choices are not deceptive... I think your understanding of Emptiness is wrong. When you realise that none of the five aggregates are me , mine or myself then you feel dispassionate towards them that is when you experience emptiness... emptiness itself doesn’t require moral qualification but it is step required to reach the goal of equanimity towards all.