Well-said, and great discussion.
MSM is the preferred term used by public health and medical fields to identify exactly that - men having sex with men - specifically since many msm do not identify as gay, bi, queer, or any other collective community term.
All-male is similarly a good term for an establishment that wants to welcome all men, without regard to how people identify themselves. I find it interesting that all-male can sometimes imply a gay following, or could also be used to imply male but not gay.
But regarding the book - I do think that it is really gay men who identify with the term barebacking, as an intentional choice for having sex. Some stigmatize it as wrong, or taboo, while others of us glamorize it; Either way, it is only the gay world that has created the hype around it. I don't think that straight men, even those having sex with other men (without condoms), think about the terminology for what they are doing, as they just consider it the normal way of having sex. I think it highlights the double standard. Look at porn - straight porn does not identify itself as "bareback" or "safer sex" - it just is what it is - and that is usually sans latex.
Language is a powerful tool. And it is great to think about how we use it.