There is no tenet about atheism that precludes distaste for others' religious predilections because there are no tenets in atheism at all. Therefore, any atheist is a true atheist so long as he or she is convicted that there is no deity.
Also see: no true Scotsman fallacy.
On the contrary, many atheists care very much, especially those that tend to view religion as harmful.
Religion seems to be universal, owing to the heuristic nature of human abstract thinking (i.e. we prefer gut feelings over logic) and there are more religions than stars, however equally arbitrary because Jesus didn't have the Internet to let everyone know he was the only one.
Hostility at least in the LGBT community would logically stem from the callousness many, or shall I say most, have faced from some religious people in our lives, not to mention the overall liberal tendencies owing to our strong presence in urban centers. So we are calloused against religion in general.