A boycott will not affect Disney at all. Barely a scratch. It will only make GOTG3 not be "super successful" but OK. Nothing that Disney will not drown in other success stories. The stars of the movie and the crew will only be seen as haz-beens. The relative failure will be penned on the GOTG fatigue or some such. Disney will not be hurt by this. But innocent people will, And to a much larger extent. So yes, a boycott is a big no no and will have only negative reprucussions for everyone.
I mean, this could be said for everything. Not buying an iPhone because they produce them in inhuman conditions? It's the low-level workers that pay for it if anything, certainly not the millionaire execs. Not buying a PlayStation because Sony hates crossplay? It's not like Kaz or someone well-known will lose their job over it. You don't like multinationals so you don't eat at McDonald's? If anything happens, it'll be local restaurants closing with people losing their jobs, it's not the higher-ups that take the heat.
This guy said some bad shit. Some people are okay with the fact he's since moved on from being that person, or at least really want to believe so as they enjoy this person's art. Other people will not be okay with what he once said or did, and are perfectly free to boycott to their liking. Let's say all people who posted in this thread boycott the movie: it still makes no major difference in the grand scheme of things, that'd be less than 1% on the revenue. However, everyone is free to act to their liking and follow their own morals. Some people are okay with supporting this guy, others are not. It's not about results, it's about your personal knowledge that you're funding something you agree or disagree with.