We can't stop the cycles of history. The best thing to do for our own mental health is to be passive observers, casually giggling as the world alternates between going to hell, and temporarily recovering.
Barring that, if you believe that fiction will help lead to the rise of the next Hitler, your problem should be with content creators, not people's reactions to the content.
Not even remotely and this is at the core of the en masse backlash you got for your comments. I was far from alone in that, on the contrary my responses have been notable for their relative lack of confrontation, being characterised more by an open dismissal of that which seemed unworthy of the effort. That being said if we are to continue down this line perhaps I should address some of your points directly.
Art, even within the popular culture, reflects and examines aspects of humanity. In turn how we interpret that art informs the way we ask questions of ourselves.
There was nothing about the portrayal of Thanos that was morally ambiguous as far as anyone else I've spoke to here, irl or on any other forum has seen, only you have drawn that conclusion. You have then equated it to real world events both by allegory, whether intentional or otherwise, and by analogy and gone on to affect an unconvincing pretence of what others here have termed psychopathy with regard to both contexts.
That you then equate the emotional and ethical implications of such scenarios to that of hunting deer (I don't intend to be sidetracked into how even the most basic ecological grounding would give the lie to the deer hunting argument anyway) and then make strength synonymous with "superiority" only reinforces self projection you affect of emotional and ethical detachments in both contexts which lends nothing to either your stated points or your credibility.
However, where this really becomes a problem is when you move from abstractedly equating fictional characters with animals and make the case that the analogous (not to mention apparently cyclical and unavoidable) treatment of learning disabled people in the real world is a reasonable cause for gallows humour to protect the mental health of the observer.
Speaking as a mental health professional who fully appreciates the value of humour as a coping mechanism I still feel the need to dispute this position in the most robust terms. Nothing about the stigma and mistreatment of minority groups is either unavoidable or a source of "giggles". The sequential path from exclusion to disempowerment through to dehumanisation is highly influenced by public perception and arguments such as the one you have presented have been at the heart of leading society down that path many times. We should not accept genocide as an unfortunate necessity to be laughed off, we should challenge the very preconceptions that make it possible in the first place.
The problem is not with the creators, nor their art, nor even your interpretation (distasteful though it may be), it is in the justifications that have impact outside of that artistic environment.