Mostly because of my personal experiences. In Belgium, as you both know no doubt, gay marriage has been legal for, hm, about seven years now, I believe, homophobia is frowned upon very heavily (except among Muslims, but okay, let's not go there), in short we're a pretty good country for gay rights. And in universities, I'm not aware of there being any real issues for gay students. But in the high schools? In my school - a Catholic school, yes, but over 60% of Flemish students goes to nominally Catholic schools, and the large majority of those schools wouldn't even dare to show the slightest indication of homophobia - there were exactly two students who came out while I was there. Two. They weren't bullied that I know of (though as I didn't know either one personally, who can say), but it's rather significant that the many others there must have been apparently didn't dare or weren't read to come out yet. Ironically, I get the impression that in many American schools there are far more students coming out.

And those suicide rates among gay teens being so much higher than those of their straight peers, that is the case here as well.

So, you know, one shouldn't exaggerate the importance of religious anti-gay bigotry in determining these statistics.