Atheists (myself included) often go off quite vocally because we percieve ourselves (according to statistics, anyway) as vastly in the minority in the united states, and we are trying to make our voices be heard.
The religious vs. the atheists for who's nicer though? Anybody's call. Some who are atheists are that out of bitterness. They abandon a god who they feel abandonded them for some reason, some hurt they had in the past. These people tend to not be the nicest people anyway. Other atheists, myself included, simply look and see no need for god. The universe doesn't seem to need one. All the religions tell us they're the only one and the others are all lies, which makes it dreadfully difficult to figure out which one is supposedly telling the truth, and what if it's one nobody believes in anymore? Perhaps I should be following the god of my ancestors...Odin, now THAT was a god. There's a thought, for instance. Then, we go ahead and see all the harm caused in the name of religions over the years, and just think mankind would simply be better off without this bullshit that lets hucksters make off with the hard-earned money of the less educated, while politicians gain power on the lives lost who think they're going to something better, when all they have ahead of them is being wormfood, which is the real tragedy of religion. It makes life, the most precious thing we have on earth, the only one we ever get, an ok thing to lose. I love life too much to play catch with it with an imaginary friend.
Honestly, I wish there were a god, I wish he would bring justice and mercy and right all wrongs, but that's why it's called wishfull thinking.
Now, relgious people on the other hand, I have met plenty who are nice, but what turns me off are the hypocrits. If I meet a bitter atheist, I feel sorry for them, because I'm sure they were hurt somehow, but I'm much less sorry for hypocrits who spout off at the mouth about their own personal holiness, but can't walk the walk. I think on the whole, religions teach some good things, but often the people who use religion are much less than nice.