You also have to remember that many times younger guys insult each other AS part of "being a dude." As in calling each other f**s (which I hate just as much as I hate using the n-word to mean "bro") or laughing at each other for being feminine. It's not a GOOD thing, but it may not be aimed at you all the time. I taught high school, and guys joked like this all the time. Men often insult each other in a "bro" way, too, and while they SHOULDN'T use feminine descriptors as an insult, it's ingrained in them since they were kids and their Little League coach yelled that they "run like girls" and said "come on, ladies, pick up the pace!" So sometimes it may not be that they are actually perceiving you as more effeminate than them but that they are including you as one of the boys.
As for having to talk "stupid" to be masculine, well, that's a particular group--not all men talk about football or make dumb jokes all the time. But you may need new friends if you don't want to talk about these things and want to fit in with them. I would say that most single guys talk about women (or men if they are gay) a lot, but then women talk about the people they are attracted to a lot as well. That's the norm for single people, I think, and with guys there is an added element of having a very strong sex drive thanks to testosterone. Heck, all I ever talk about these days is sex! (Thanks, T!)