If you expect a Christian on a site full of atheists to have to be thick-skinned, then by the same logic, you should expect an atheist in a high school full of Christians to be thick skinned. I don't think either of those conclusions is acceptable.
Are you thinking of the same reddit? It's a web site of funny videos, pictures of cats, rage comics, memes, and stupid jokes, and the occasional groupthink. 18 of the 25 front page links are imgur. Of the remaining 7, four are dumb discussions on reddit. One is a news article about the reddit founder (random crime story; otherwise uninteresting). One is a news link on youtube of actual news (if somewhat biased), and one is a link to an interesting study. Depending on how you count, that's 4-8% useful content. When you get into comments, it's even dumber.
reddit had a community of inquisitive, intellectual, creative individuals when it was formed at Harvard. Over time, the idiots and the bigots moved in, and right now it's a web site for wasting time on stupid amusements.
I was listening to right wing talk radio on a long car drive a few months back. What struct me was that the host, who mostly spewed venomous lies, would constantly refer to his viewers by some term (I forget the exact wording) like "the best and the brightest." I feel like reddit users are the left-wing equivalent of that. Clueless groupthink, combined with a very high opinion of themselves.
As an atheist, you're also free to move to a different country if Christianity bother you. US is 76.8% Christian. China is officially atheist. The only reason you're interested in this country is because it was founded on the Puritan work ethic, and has a very high level of social capital coming from Judeochristian values. But you shouldn't stay here and bitch about it. Same thing with blacks trying to go to the (better) white schools in the South prior to Brown vs. Board of Education -- they had their own place where they'd be accepted. Have fun with that logic.
Bigotry doesn't belong anywhere, even if people are free to leave. Intolerance hurts atheists more than it does Christians, and you're an idiot for endorsing it.
The stuff that gets to the frontpage is there because it's the most commonly appealing thing in the largest original subreddit communities (r/pics, etc). The intelligent discussions happen behind the scenes, on the small to medium sized subreddits. Anyone that's been on reddit for more than a week understands this.
By that token, there are, without a doubt, plenty of smart people on reddit. They are, as your comment implies, a tiny minority, confined to a few subreddits (and those are mostly characterized by groupthink -- e.g. any conservative comment on most liberal subreddits will get voted down, no matter how intelligent and well thought out). The front page is defined by what most people vote for, and that's rage comics, misogyny, with the occasional sprinkling of anti-Christian bigotry (this used to be more prominent, but the average IQ has dropped to the point where r/atheism is beginning to look smart). That's representative of the average reddit user.
All that said, I'm not looking for anything on the front page beyond a way to waste a bit of time. When I first joined reddit, I looked to it for intelligent articles. Later, I looked to it for amusement. Now, I look to it less and less, since memes aren't the same thing as wit.