Can a man just turn gay over night?

Just curious to know, this guy has been hitting on my man at work, my man doesn't think he is hitting on him and says the guy isn't gay, but he says stuff to him like, I wanna bite you and you look good in those pants and even flashed his weiner at him one day to show his spiderweb head tattoo! Sounds all too weird to me and my b/f thinks it is cool and is acting really weird about the whole thing like he likes it. My b/f usually has a "scruffy" kinda look to him and today he went to work clean shaven and smelling good! Should I be worried?