Stories and teachings that glorify adult children and speak against toxic parenting

A bad example is still one to learn from. We can learn from others' mistakes. And in this way, we can understand that what the Buddha said is still true:

iti106:3.2: ‘First teachers’ is a term for your parents.

Over our lifetimes, we encounter many teachers. Some may have taught us with awareness. Others may have taught us by their mistakes. And however it is that we learn, it makes sense to acknowledge that time of learning, that gift of wisdom that passed on to us.

The Buddha had many teachers. He listened and practiced carefully, deciding for himself what was skillful and leading to peace. And when he learned all he could from his teachers, he would take his leave to seek deeper knowledge.

MN26:15.34: Then it occurred to me,
MN26:15.35: ‘This teaching doesn’t lead to disillusionment, dispassion, cessation, peace, insight, awakening, and extinguishment. It only leads as far as rebirth in the dimension of nothingness.’
MN26:15.36: Realizing that this teaching was inadequate, I left disappointed.
MN26:16.1: I set out to discover what is skillful, seeking the supreme state of sublime peace. I approached Uddaka, son of Rāma, and said to him,
MN26:16.2: ‘Reverend, I wish to lead the spiritual life in this teaching and training.’

If a teaching is inadequate, we leave disappointed. Yet in that leaving, we will still need to remember and acknowledge the lessons learned. If a teacher is toxic, then we have learned the dangers of toxicity. And if we forget those lessons, then we run the danger of being toxic ourselves. There is no glorification here, however. There is a simple acknowledgement of what was learned.

So let us seek and share the skillful that brings us peace, acknowledging the skillful lessons learned from all our teachers, starting with our parents, the first teachers.

Yes. There is a teaching from the Buddha that is very practical about this.

He exhorts you to be the son or daughter who is superior to their unvirtuous parents.

“Now what, bhikkhus, is the superior kind of son? In this instance a son has a mother and father who have not gone for refuge to the Buddha, to the Dhamma, and to the Sangha; who do not abstain from taking life, from taking what has not been given, from wrong conduct in sensual desires, from false speech, and from intoxicating drink leading to negligence;who are unvirtuous and of bad conduct. But the son is one who has gone for refuge to the Buddha, to the Dhamma, and to the Sangha; who abstains from taking life, from taking what has not been given, from wrong conduct in sensual desires, from false speech, and from intoxicating drink leading to negligence; who is virtuous and of good conduct. This, bhikkhus, is the superior kind of son.
Iti 74

However, you can still help your unvirtuous parents by introducing them to the Dhamma, the Buddha's teachings, which is the greatest gift in the world (Iti 100).

"I tell you, monks, there are two people who are not easy to repay. Which two? Your mother & father. Even if you were to carry your mother on one shoulder & your father on the other shoulder for 100 years, and were to look after them by anointing, massaging, bathing, & rubbing their limbs, and they were to defecate & urinate right there [on your shoulders], you would not in that way pay or repay your parents. If you were to establish your mother & father in absolute sovereignty over this great earth, abounding in the seven treasures, you would not in that way pay or repay your parents. Why is that? Mother & father do much for their children. They care for them, they nourish them, they introduce them to this world. But anyone who rouses his unbelieving mother & father, settles & establishes them in conviction; rouses his unvirtuous mother & father, settles & establishes them in virtue; rouses his stingy mother & father, settles & establishes them in generosity; rouses his foolish mother & father, settles & establishes them in discernment: To this extent one pays & repays one's mother & father."
AN 2.32

However, if they are not interested in listening to the Dhamma, don't waste your time.

Now at that time Venerable Kassapagotta, having withdrawn for his day’s meditation, tried to advise a tribal hunter. Then the deity haunting that forest approached Kassapagotta wanting to stir him up, and recited these verses:

“A tribal hunter wandering the rugged hills
is unintelligent, unthinking.
It’s a waste of time to advise him;
this mendicant seems to me like an idiot.

The tribal hunter listens without understanding,
he looks without seeing.
Though the teaching is spoken,
the fool doesn’t get it.

Even if you lit ten lamps
and brought them to him, Kassapa,
he wouldn’t see anything,
for he has no eyes to see.”

Impelled by that deity, Venerable Kassapagotta was struck with a sense of urgency.
SN 9.3