Why do people assume that I am a republican when I say I believe in God?

I am just curious as to why I am singled out because I am not a republican. Let's not get into the abortion/gay issue because that honestly shouldn't be the only reason you vote for a guy (among other reasons). Honestly, neither side even really cares and only uses those viewpoints as a convenient way to gather support from either side. In my eyes, voting is choosing the less of two evils.. but I digress, why am I soooo bad for not being republican?