Of course it should be taught, but only at high school and college levels, when (most) students can make decisions for themselves and classes are voluntary.
Whether you're a devout believer or just someone who thinks that religion is the most destructive invention man has ever created, there is no denying that it's a huge part of human studies. Practically every culture has a dominant religion; you can better understand a culture if you understand their belief system.
I can't even see atheists having a problem with Religious Studies. To them, it's just another mythology class.
I personally find the whole subject extremely fascinating.
EDIT: Now that I look at Havoc's post again, I think I completely misinterpreted what he was trying to say, but that's OK because I think my little shpeel on Religious Studies is still relevant. XP