Whatever the case, he ultimately made those tweets. A comment I read elsewhere on a story about this was quite good, it simply asked "if this firing was about the director of 50 shades freed would anyone care or want him re-hired?" I think that rings true, the fact is James Gunn has made two very popular superhero films that are part of a very popular superhero saga and that will make people more sypathetic to him, myself included.
I don't like the way dirt is being dug up on people from years ago, provided what they did is not illegal of course, and it's not just James Gunn who has been had this way, but he is ultimately responsable for what he tweeted no matter how I personally view it, and the political climate across the west dictatd that he would lose his job for it.
There is a big responsability to using social media, infact a huge responsability to using it. It's a really good lesson for everyone, what you post online can come back to haunt you years later. If you have any ambition, be careful what you post. I have a dark sense of humour, the boundaries I stick to online are far far lower than what I will say to a close friend.