The history shows clear evidence that there was a rollback war, as you already saw. Meanwhile the comments raised several strong objections to the inclusion, ranging from the commentary was baseless to the commentary was unrelated to the actual question (myself included). The original author continually insisted on including the content. Eventually, a moderator tried disassociating the post from the author. The same moderator originally deleted references to Trump, but when the author edited in a few quotations (even after being disassociated), the mod apparently decided to leave that alone. It goes without saying, but there were a few wipes of the comments on that answer along the way as well. The users involved left it at that and moved on. (I don't think anyone was really satisfied with the final outcome.)
The Trump content
But since the discussion has been reopened, the content about Trump has no place there, regardless of your political leanings.
To start with, there's nothing in the material posted that directly links anything about the policies Trump advocates or his personal life to the censorship in the movie; the post just gives a broad, vague dislike for Trump by the people involved in making the film. There is no mention of Trump censoring anyone, much less any actual evidence he advocates for doing so. There's not even evidence that anyone thinks he would implement censorship, except for possibly the post author. Additionally, at the time the film was in production, the Trump campaign didn't even exist yet (Even the actress quoted refused to believe Trump was seriously campaigning!), so the idea that the people behind the movie had Trump specifically in mind for any political action in the movie is fairly unreasonable.
Worse, this content is also clearly inflammatory. I'll borrow DVK's words, since I can't put it any better myself:
The answerer implied that Trump is equivalent to a genocidal dictatorship that kills children for political purposes. The fact that they used personal opinions of actors (which are off topic to the question 100%) and not just their own personal opinion is irrelevant. For comparison, consider someone posting anti-Obama slur based on Clint Eastwood's opinion, in a question that is 100% irrelevant to Obama or Eastwood as an person.
(Minor corrections to spelling made above.)
StackExchange as a general practice strives to avoid these kinds of conflicts between their users. For starters, we have the Be Nice policy, which applies to public figures as rand al'thor mentions. This content arguably violates several clauses:
- Rudeness and belittling language are not okay: comparing someone to a totalitarian, murderous regime without any actual evidence does not foster respect. If it could be shown to be a relevant view held by someone involved in production, then it could be presented that way. But there's no clear link between the views and the original question, and the post author espouses it as a personal view they share.
- Be welcoming, be patient, and assume good intentions: I think it's pretty obvious that this violates the "good intentions" part without evidence.
- Bigotry of any kind: This one is debatable, but you could certainly make a case that this is likely to alienate users with a particular political viewpoint. Again, if it were just presenting someone else's view and clearly linking it back to the question, that would be different.
I'd also like to point to a relevant meta post by Shog on the SciFi StackExchange. Shog is specifically addressing a chat room going off the rails, but he lays out several general principles we can apply to any part of the sites. Here's what I think is the most relevant part:
In a public place, in a diverse group, it can be all but impossible to know what someone else will find off-putting. If you care about the people around you, the best you can do in most cases is to listen and watch for signs that they've become uncomfortable and, when you observe this, to back off: stop the conversation and either move to a different topic or move the conversation to a different space.
The fact an argument and edit war (and now a meta post with further argument) erupted over this post gives solid evidence we're dealing with a situation like that. Again, we must combine that with the facts that the author offered it as their own opinion and did not provide clear evidence that it influenced the production of the movie (or the book it was based on). If it were presented more objectively and gave strong evidence that it actually related to the censorship in the movie, we would be dealing with a very different situation.
Even worse, the answer included Trump commentary from revision 1 and didn't even attempt to provide any kind of source material to demonstrate its relevance until after several rollbacks in the edit war. Even after providing some kind of source material, the answer still failed to demonstrate its relevance to the question at hand. All this very strongly suggests that the author just wanted to slip in their personal negative opinion of Trump. If that wasn't their intention, they didn't demonstrate their actual intention very well.
How to handle it
Everyone involved is of course entitled to their opinion on Trump as president, including the post author, moderators, readers, actors/actresses, directors, and anyone else. And they're entitled to express their viewpoint. However, there is a proper venue to do so, and StackExchange has made it very clear they do not want content that needlessly incites arguments. When inflammatory opinions are demonstrably relevant, post authors must at least attempt to give objective, impartial analysis and presentation. They should also be very receptive to feedback in the interest of minimizing conflict. That plainly wasn't done here.
Bottom line: the content should have gone long ago and still should be removed. (At the time of writing, it has since been edited out again. It should remain that way.)