As for my thoughts on it, I think people are misinterpreting it horribly and blowing it way out of proportion. What they don't realize is that Richards is not a standup, per se, and didn't have any idea what to do when he was heckled onstage- which, by the way, is one of the worst experiences a person can have short of being killed. Try it sometime.
So a couple of black guys heckle him all night and finally he just snaps (this is the only part we're shown on the video) and since he's an actor and not a wit or a think on his feet guy, he has nothing to do but say the simplest thing that comes to mind, and attack the hecklers with the only thing he knows about them- they're black. He completely freaked out and lost his cool, and went nuts, but he's probably not racist, and what he did isn't that horrible, except in what it will result in in his own life. I would say heckling someone mercilessly while he bombs onstage is worse than what Richards did, which was a desperate man shouting ANYTHING he could to try to regain his dignity and take away the dignity of the people who were doing that to him. That's the key here- "nigger" is a word whose power exists because it makes a person feel subhuman instantly. That's why it's a powerful word. Richards alludes to this himself late in the video. Heckling someone onstage like that as he bombs and is humiliated and struggles in front of all those people has the same impact as calling someone a nigger- it dehumanizes and degrades and humiliates. Richards had a readymade response to the hecklers, and so he responded in kind. It just happened to be an un-PC response, and unfortunate. But as far as which act was meaner, or more offense to me personally, I'd say it's not even close- heckling someone is far meaner, and hecklers, of any color or creed, ARE subhuman, and deserve to be made to feel bad about themselves. It's simply one of the cruellest acts there is, doing that to someone while he's up onstage like that.
You can see if you watch the video, also, that Richards when he freaks out goes into a theater-trained la la land. He is not a standup, again, but theater trained. When he freaks out and panics he begins getting very theatrical and using physical flourishes and mumbling things in an English accent, a theater twang. In fact he goes into a character, which is not being reported in the press about this incident. All the press is saying he yelled "It's a nigger!" several times at the black audience members, which is not true. He addressed them with the reference to "50 years ago such and such would've happened" and then went into character and turned away from them and began pantomiming white hillfolk's reaction to seeing a black man lynched, and that's when he pointed and shouted "it's a nigger" several times.
One must also remember that Richards, being unfamiliar onstage but having some familiarity with modern comedy clubs and what material people use there, was likely influenced by how frankly racist and horrible and free to say anything so many modern popular acts are. Panicking, in a bad spot, he tried to go in that vein, but through sheer lack of understanding of what's allowed and what's not, and how it's allowed, he ended up with this.
To sum up, I think he has definite anger issues (and possible mental issues otherwise), and is probably not particularly familiar with black culture or black people, but is likely no more racist than the average white person. Lay off the poor bastard and save your vitriol for people who actually hurt, or hate, other people.