Really? Because people online need to be diehard fans to overreact to something?
And honestly, it wasn't all that big of a reaction, compared to what happens when people mess with popular characters. I don't know if you were reading the hype in 2007/2008 when the first pics of the Joker were released, but THAT is what it looks like when a popular character is messed with.
If you weren't here, let me sum it up: Anarchy. Seriously, the internet blew up. Within a day you had people forming two groups, there was one thread that proclaimed "I have faith in Chris Nolan" and one saying "I don't have faith in Chris Nolan." Brokebat mountain comments raged, people called the character Panda-eyes, said it looked like he was wearing bad lipstick etc. etc. And then when it became apparent he might be wearing makeup, the permawhite debates started, and lasted for months.
I'm not exaggerating with this either, they literally went on for months, right up until the movie came out. You had people saying that Nolan was going to make things too realistic, that the Joker wouldn't even have green hair probably, etc. etc.
It was insane. And the arguments would spill into the other boards all the time. Because the Joker is an A-list villain, and people cared about the character.
With the Mandarin, we got a little blip. Because, let's be honest, nobody really cares about the Mandarin. People were more pissed because Kingsley's performance as the Mandarin looked like it was going to be awesome, and we got shortchanged on that. I definitely felt that way. But I didn't really care that they changed the character.