Some people are just really stupid and make all Christians look bad
It isn't so much that they're bad, but they're following a system which primarily causes evil. I see many religious individuals referencing atheism as some sort of disease. I also see many people considering it to be a religion. To begin with, if you're monotheistic or polytheistic, you're not religious. It's a single belief, not an entire set of guidelines. Now, while I cannot consider myself to be atheist because I believe in the lack thereof what isn't absolute fact (though the Christian god, according to the bible's own inproper statements is, in fact, just as "real" as my imaginary friend bill), I still condone entirely a single belief. However, if you base this belief around a religion/etc, and you do not follow the rest of said system, you do not follow the absolute word of it, implying its credibility to be absolute 0. It's like going through a contract and thinking it's appropriate to only act on one of the items listed, even after signing it.