Is reddit supporting racism/sexism by not casting out those who say those sort of things?

First off, apologies for the title. I suck at making titles

I've been debating with a friend of mine (who hates reddit) about why he doesn't like reddit. His main contention is that reddit allows for stuff like the various jailbait reddits. He also said (to use his words):

"reddit, by not casting out “shitty, racist, sexist, bigoted” people is in a small way supporting their behavior by giving them a voice. Those voices need to be marginalized and ridiculed and demeaned, because otherwise, they will in their own way think that their terrible opinions and behavior are actually acceptable, when they’re not."

I don't actually know a good way to respond to this. So, I turn it over to you guys. What's the response to this?

(edited for clairty)

Edit 2: I've posted his response in the comments below, but in case it doesn't get seen, here it is again.

"Just took a quick look at it, and at least in the beginning it's more civil than I figured, but as usual they don't get it.

It's not about blocking all of their posts. Yes, those people have a right to say that horrible crap. The other peo...ple have a right, and a duty, I feel, to make those people better people by not supporting their assholery. Some guy brought up the Westboro jackasses, but the thing is, America has marginalized them. You don't see newspapers putting their opinions on the front page or anything like that, as if they endorse them.

What happened on reddit in that thread is that they, by not downvoting those posts and not upvoting the good ones, have allowed all the bullshit to be front and center, in the equivalent of the New York Times letting Fred Phelps (I believe that's his name) post an opinion on God Hates Fags on the front page, without any disclaimer from the editor or anything like that.

Are you telling me there wouldn't, and shouldn't, be an outrage if something like that happened?

What these people are forgetting is that freedom of speech is a right, but it's a right we should use responsibly. It makes us better people when we do so. There are numerous examples of where you have the right to say something, but it would be better of you to say something else. You can call someone a dirty bitch Nazi in an argument about feminism, but other people in the argument should call you out on how stupid and immature that is.

When they don't, it creates an atmosphere where that shit is okay. I don't want to live in a world where people are allowed to go around talking about implied anal rape to a 15-year old (seriously, some of those comments made me shudder) and then to have a bunch of self-righteous "internet kids" come in and go "freedom of speech, man!"

I guess we can go around using racial slurs, too! Freedom of speech! Fucking idiots."

The whole thing started over the this thread in r/Atheism.

http://www.reddit.com/r/atheism/comments/nq7s4/what_my_super_religious_mother_got_me_for