Hmmm, yes. Nothing quite pulls you out of the moment like reading about someone's thrusting man-meat pounding a gaping fuck-hole.

Unless it's a leaky cock. What, he's got the clap? He's incontinent? Either way, keep that pelvis far from me (to quote Betty Rizzo).

Actually, I have read the latter in fics by some of my favorite authors, so perhaps that particular squick is not shared.