I could try to write a post about the issues I have with religion, but The Oatmeal does it so much more eloquently.
As Matthew Inman states, I don't have a problem with anyone practicing religion themselves, just don't be an asshole about it and try to force it upon others.
Check out the full post here, but a few highlights and some of my biggest peeves:
P.S. Aggressive Door-to-door, Bike-riding Jewish Missionaries would be awesome.