They'll probably just get Taika Waititi to replace him

How can anyone defend what is happening to him?

He made some tasteless jokes a decade ago, got called out on it and apologized. In the 10 years since he has matured and is now a different person.

Can I be honest, 10 years ago when I was 17 years old, I would sing the lyrics of my favorite rap songs without excl. the n-word. I was not a racist - I was stupid, careless and ignorant. In 2010 when I got together with my ex-girlfriend, she told me not to sing the word and explained why. I apologized and never did it again. I learned from my mistake and matured. Would it be fair that I lost everything today because of what I did 10 years ago?

I don't see how anyone can be surprised that DISNEY reacted when tweets encouraging (even if just for "fun") PEDOPHILIA, CHILD-MOLESTATION and RAPE were brought up and bad press started to emerge in mainstream media. Together with racism, that's literally the last thing they want to be associated with. I'm just gonna post this again.

No, that wouldn't be fair, but I also think it's pretty damn silly that you genuinely think singing a word is a huge mistake and that you've evolved as a person by not doing it anymore. Putting that much weight into a word - especially one you're just repeating from the lyrics - is a clear sign of what's wrong with today's society.

Also, again, the reason I'm "defending" what's happening to him is because he wanted this for others. He was gloating smugly when others got fired for dumb stuff they'd tweeted. Now the shoe's on the other foot. Credit to him that he's not whining about unfair treatment, he's taking it and saying he understands Disney. But his fans are not.

Oh no he made a joke 10 years ago. I say he should be hanged by his neck until hes dead.

It's really telling that the best argument you can come up with is to summon a bogeyman that did it first.
Especially since you're willing to let go of your conviction that saying bad words doesn't matter, just because you don't like the guy. Flip-flopping much?

FTFY.

Bold: Lol. Something tells me James Gunn will be fine.

I'd say that the biggest concern is people abusing poor PR policies to get people silenced, a tactic they plan to use again and again. 
That a PizzaGater can get this much hold public attention is maybe more important than Gunn's net worth.

1. The 10k plus things he said were pretty bad. Pedo jokes/"provocative" pedo comments.

2. He worked for Disney who provides entertainment to kids.

3. This is applying the left's own rulebook to itself and holding them to it.

4. By his own remarks about Rosanne, he agrees with Disney firing him for his posts in social media. 

1) The people purpotedly offended by this make rape jokes near constantly and are obsessed with imaginary pizza basements.
    P.S. I could find no reliable source for the 10k tweets. Seems to be pushed by PizzaGaters exclusively...
2) Disney hired him AFTER both the tweets, and the apology for said tweets. 
3) As I've already highlighted this is a pretty piss excuse, but it's worth noting that scouring for old tweets usually comes after the person behaviour and actions in the now.
    Nothing about Gunn's tenure under Disney would suggest those tweets to be relevant, or that people bringing them up have any issue with them. 
    It was an excuse to get a political opponent fired.
4) Roseanne made her openly racists remarks AFTER being hired, not before. Her entire tenure, past public history, and subsequent actions ("I thought the BITCH was white") would            suggest she was a liability. The tweets were an obvious manifestation of her actual problem, not some unrelated joke.