For the most part its a normall online comunity, something like a forum, and then you have /b/ and /pol/ , everything bad that you hear about is probably caused by /b/ and /pol/
I frequent /b/ because its fun although everyone there is racist and a pedo
4chan is mostly known for its raids
There are a lot of racists and pedos in /b/, but most are probably just trolling. Either that or it changed a lot since I last visited.
It's not something that should be taken seriously, most of the time 4chan is involved in internet pranks and deliberately pissing off people who have absolutely no sense of humour. Sure, don't get me wrong, it's the internet there might be some real racists and peadophiles somewhere but that's like real life, but the only reason it might be 'rife' in a community is precisely to mess with people who don't do their research or check this stuff out properly. Much of what the internet does involves pranking very serious people who are forced to respond seriously to the things they say, at which point there are other stupid people who take these people on their word and blow things completely out of proportion.
By the way, Cass LeChat is a perfect example of the kind of person these kinds of pranks and trolling attempts are targeted at.