Prob a little self cons about making an effort to look good when seeing a "mate" (after all, it is not cool to make an effort to look good for your same sex friend if you are hetero - .............joking!!!!!), and therefore making a joke defuses this. Nothing to ponder about too much tho as us guy's are not as complex as you girls think
I joke about a lot of things with my gf, brother and friends, sometimes of this nature. It is a boy thing to joke in this manner, especially when making the time or effort to see friends. I meet up with my old surfing buddies from Queensland a few times a year to have a week of surfing and catch up, and all those guys are definately "bitches" , 'man-lovers' and 'man-whores' and my gf and brother know that i am talking about my surf buddies when I use these terms (note this type of gangster rap language (yo, yo!!)

makes up very little of my regular conversation!). Sometimes my mates and I even use this type of language and interaction with each other when involved in Tom Foolery.
Great to hear that you encourage the space for your bf to do his own thing (and for you also). Nothing worse then to hear the generical male and his tale of woe of being "under the tumb" of his gf who acts as a handbrake for all of his pre-spouse interests.
P.S. My brother is a "bitch" also, but I don't make an effort dress up for him tho.
Bunnyboy