Disney could have worse problems than pushy Marvel fans if the alt-right decides to go after Lin-Manuel Miranda during the mid-term elections. They'd be attacking him for his support of President Obama's commutation of Oscar Lopez Rivera's sentence. Rivera was one of the leaders of FALN, a group of communist Puerto Rican separatists who went on a bombing spree in the continental US in the late seventies, causing the deaths of five people.
This sounds like a conspiracy theory, but it was an actual news story about a year and half ago:
https://www.newsweek.com/oscar-lopez-rivera-terrorist-some-hero-others-621949
It just got overshadowed by the fact that Obama had commuted Chelsea Manning's sentence at the same time, and his opponents prefered to focus on that. I don't see the Republicans not bringing it up again now, though. It's too good a way to paint the Democrats as weak on border security, soft on communism, and generally anti-American.
After the success the alt-right had with Gunn, they'd definitely try to involve Disney through the Mary Poppins movie, and they wouldn't want to settle for anything less than a firing. The thing is, I don't think Disney could fire Miranda even if they wanted to. He finished shooting months ago, his part sounds too big to cut, and as for reshooting his scenes, who could they find both able and willing to take the job?