Many comedians and comedy shows have made successful jokes about all kinds of terrible things, including pedophilia and rape. People laugh because A, the joke is well constructed and funny, and B, because they know this a comedy show and not the real world. Gina wasn't doing a bit, she wasn't having a laugh or satirizing anything. She was making a statement. A statement that goes against her employer's policies.
Also, to compare Gunn and her is idiotic. Gunn did these things decades ago, when edge humor was in. Everyone wanted to be Daniel Tosh and Dane Cook. Gunn was just REALLY bad at it. When they surfaced the first time, Disney told him this can never happen again. And it didn't. Ever. Gina was told to cut it out in November. Less than 4 months later and she's doing it again. That's a friable offense.
When Gunn was fired, it was because Conservatives were angry over Rosanne, so they brought up old news and made a stink about it. Disney was dumb and caved despite already forgiving Gunn for these tweets and Gunn being diligent about not repeating the long outgrown offense.
One is going through someone's history searching for things out of context to hang them by. The other is someone saying something and not liking the reaction they get. Gina was a moron. Not because of her views, although they are pretty dumb, but because she blew her shot by running her mouth on twitter.