he keeps going on about how religion is the worst thing ever.

Well, it is :P

But that's beside the point. Imagine the scenario without the religious angle. He's meeting your parents for the first time and they get half way through introductions before he loudly belches in their face. That's not dating material right there. That's an asshole.

My cousin had warned me about dating an atheist but considering i don't take religion too seriously I didn't think it would be an issue. Maybe I was wrong and I'm not compatible.

Don't let this asshole cloud your judgement on the issue but dating outside of your faith does have potential pitfalls. You will need to be able to listen to them speak their minds on any topic and that is something hard for some people to do when the topic is close to their heart and the other person dismisses it. Whether it be religion, politics or favourite pokemon, if someone incorporates it as part of their identity listening to someone else describe it as baloney without taking it as a personal offence takes a certain amount of open mindedness and intellectual integrity.

Then you have the other minefields of things like religion intruding it's way into familly. What about getting married in a church by a pastor? As an atheist I would feel like that would tarnish my wedding just a bit if I had to effectively lie to keep up with appearances while making vows. What about Christenings? Some families get rabbid about that. If they actually believed that an innocent child will be tortured if it's not christened it makes sense they would do anything including kidnap to make sure it happens. I would certainly do whatever it takes to prevent a kid being tortured but from an outside perspective I would not allow a child of mine to be claimed by someone who believed that this was "just". I've heard stories about famillies getting ripped apart because the grand parents demand that a kid be christened.

Religion can be more insiduous than you would think and turn good people nasty in ways you might not forsee over triggers that don't make sense. If I loved a religious person I would probably listen to my heart but if I was looking for romance I would listen to my head and avoid like the plague.