Why do people think all atheists are for gay marriages?

Personally, I see no reason to redefine a word which has meant the union of a man and a woman for something like 4000 years. I don't believe in sacraficing the language on the alter of political correctness. Me thinks this is one of the things george orwell was warning about in his INGSOC world of 1984--the ministry of love is actually the ministry of hate. I have no problem with coining a new word to define that union--codifying it into law-giving equal rights--I simply think its wrong to have to redefine a word to be politically correct. So all atheists are not supporters of this issue. Are there any more like minded individuals out there that are non-believers?