Should any monastic be considered a noble one?

I think that's several questions with several answers:

• Should anyone be considered noble?
  Generally you should know for yourself what is true.
• Can I have a disagreeable attitude?
  See the Parable of the Saw.
• Can I express disagreement?
  See the Right Speech criteria.
• Can I disagree with how the Dhamma is presented?
  See the Four Great References.

Then there's the question of whether you (as a monastic or layperson) "are free to" criticise a monk's attitude or behaviour or views.

• If you're a monk then you would know the Vinaya -- which says that some monks live in dependence on a preceptor -- and which says you should ask a monk's permission before you reprove their behaviour
• If you're a layperson then your question might be whether you want to support the monk in question; I'm mindful of the doctrine (in the vinaya) that monks mustn't try to claim they're noble (even if that's true) to laypeople, because laypeople might be naturally inclined to support only the noble monks.

Should every monastic unconditionally be considered a noble one, and treated as such, to abstain from bad kamma at the very least? or are lay people, and other monastics, free to use personal judgement based on the personal qualities, or lack thereof, of a given monastic?

I think you already knew the answer. But in case you need some concrete instruction from the Buddha, check out AN 4.192, Dhp 26, SN 20.7, MN 142, etc.

Motivation is so important in all we do. Try considering what the proper motivation would be for honoring monastics? For honoring lay people... for proper attitude and treatment of others in general. Maybe if you focus on really analyzing the why you should honor a noble one... is it for their benefit?? For others benefit?? For your own benefit?? Some combination?? And really importantly how does it benefit..

With these maybe it will help you figure out the answer to the question of who?

Quite honestly should it matter what level of attainment another has for you to decide proper conduct for you towards them? If your communication is criticism of them or disagreement with them... whose well-being are you focused on with this criticism? Is it for their benefit? Is it altruistically motivated? Or do you wish to show off your knowledge? Are you worried about your own reputation or well being?

Thoroughly understanding and analyzing our own motivation is key in every action we take... the most basic question I am trying to ask myself is whose well being am I focused on with any particular action. Is it the enemy of all: the self-cherishing attitude?!

Should every monastic be considered a noble? - I think no you should not always consider such just based on the clothes a person is wearing (ie: Monk Robes). It could be anyone in the guise of a monk.

But in addition to being cautious towards anyone it is always best that you first listen to the words spoken by the said person without any bias. After listening to it if you disagree, what I do is just leave without making a commotion. As if the person who said the specific words might have had a right intention but he could have worded it wrongly and if you berate a person like that, yes you will recieve bad kamma. The best option would be to find another monastic to hear the Dhamma.

Taken that a good friend would give you advices to abstain from things which could harm you or of bad results, what advices would you give, being in such a possition, knowing that cause and effect isn't a democratical thing, or a "liberal"? Would you send him in an easy fatal lost "war" to win his favor, give into possible defilements?

While it is a very seldom gift of being well-wished adviced, even if disliking, think on you as a child and your parents, it's not something you are obligated to and so worthy to think clear why wishing to do, honest.

Just a sample, not to present something, but to have a possibility to think maybe more from outside, as life actually runs different as thought, as just one to give: Assimilating of Bhante Samahita's death, decay of beloved

For on ordinaty person it's really hard to keep preoccupations, feeling... seperated, not to speek of understanding of what possible just known from far.

So it's really not an easy issue if serious wishing to build up Nissay with those headed toward liberation, not even if after good, firm, intellectual understanding.

May all take care and often remember their parents hardship to even letting have grown till here.

For all that reason, since the old, people are adviced to focus their dedications toward the Sangha and others then the most think, the Buddha gave also to householders advices of how to react on "troublesome" monks, since thinks aren't for sure! And the Buddha knew his Pappenheimer:

...Anāthapiṇḍika the householder heard that, “They say that the Kosambī monks, quarrelsome, makers of strife, makers of disputes, makers of rumors, makers of issues in the Saṅgha, are coming to Sāvatthī.”

Then Anāthapiṇḍika the householder went to the Blessed One and, on arrival, having bowed down to him, sat to one side. As he was sitting there, he said to the Blessed One, “Lord, they say that the Kosambī monks, quarrelsome, makers of strife, makers of disputes, makers of rumors, makers of issues in the Saṅgha, are coming to Sāvatthī. How am I to behave with regard to these monks?”...The Discussion of the Eighteen Grounds

Old lay people in tradition countries, wouldn't advice or support one, nearly generally, especially if having been monks, but of course they had no google and suttacentral-monks, which might be useful or will most eternal cut of the stream of those rest heading already outward. So again, right critic leads to heaven (even if just by ones thought) and wrong likewise to hell. So the proverbs of binding a knot into your tongue aren't out of reason, one can be sure, and for good deeds one does not need to become a "killer", not even one who stuggles outwardly long. In both directions, and the rest stays open for real compassion and seldom left paramis one could have.

And to add an importand issue, kamma, and that's what the most here is about, doesn't care whether you then tell wrong just your friend, spread it cicretly or anonymuosely... a larg bypass downstairs as well, by especially "smart".

There should be no issue better to simply direct the case direct, and if no "success", onecan deside to left another off for one self, not even just at least.

(Note that this isn't given for trade, exchange, stacks or what ever binds, but for freedom from it.)