Back during it's heyday in the '80s, Mac had gorgeous women throwing themselves at him left and right, but never showed any real interest. Was he gay, or did he have a girlfriend with a testicle lockbox?
Ya' know, I'd actually buy that MacGuyver was gay. Something about the way he grinned in the intro, the even tan, and the thing that you mentioned. If he wasn't gay, perhaps he was a closet case. Oh, and the hair.
I don't think it's what the character's creators intended, mind. It was the thing in the '80's to have your male hero be the 'unapproachable lone wolf'. Which actually reinforces that whole gay idea because most guys that give off that vibe are gay.
I just remember Terri Hatcher and the only babe who had anything resembling a role as his partner absolutely falling over themselves to get him in the sack, and he blew them off. That was 20 years ago, and I was lot younger, but even now, if Terri Hatcher is throwing herself at me, I'm not going to get philosiphical about it, I'm going to find the nearest comfy spot and start removing clothing.