Certainly they can. I've worked with quite a few gay men over the year's, and for the most part, have gotten along well. (Several even confided to me that they were turned on by me.) I've lost touch with most everyone over the year's and wish I hadn't. I worked with some really good people, straight and gay.

My mother was an interior decorator and I grew up around gay men (moms "best friend" was a gay man).
I have several guys that I call friends who happen to be gay. we openly "joke" about it....sometimes, our conversations leads me to an erection and I tell them so.

Can a straight guy a straight female be friends?

That's about the same question actually. It's not like gay guys are sexual predators that hit on everything with two legs and a cock. Of course they can fall on love or be attracted, as a female friend also can be. Nothing is different.

I have two gay friends, and both of them seem much more comfortable with their self and more self secure then any of my straight male friends.