I think people are looking at this in the wrong way. Disney and the left are not the same. And Gunn certainly wasn't destroyed by the left. More than anything he was destroyed by corporate forces and our current climate. It's Disney. And it looks really bad. Yeah, it was brought up by alt right scume. But this is still bad PR and it still looks bad, it doesn't matter who brought it up, no one is forgiven for their crimes just because the right brought it up. And Disney is a massive MNC, not the left.
And Disney is still going to protect its brand, and they probably did think he deserves to be fired, but that's not the issue. You can come up with different situation and examples that didn't follow the paradigm, but everyone who is doing that is missing context. The context of these situations changes very quickly.
Post metoo corporations are more careful than ever about courting bad PR. The examples keep racking for corporations to avoid bad PR. Warners got badly burned with going with Depp. Does Disney want rape and paedophila controversy? Even if they are jokes? The risk simply cannot be worth it.
Gunn is a victim of our current circumstances, of corporations wanting to avoid controversy at almost any cost. Yes the right too, but no one is ever going to be excused of what they did simply because the right brought it up. Gunn did write those tweets, and Disney does want to avoid controversy in this current climate.