>>29038088
I think on an almost subconscious level the site of an erect cock elicits a visceral reaction of arousal in most men regardless of their orientation. Because we all know how good it feels to cum, we respond majorly to the sight of a dick blowing its load, even if it isn't ours.

Straight guys self-insert, and imagine it's their own meat gushing cocksnot. Us bis and gays usually just enjoy seeing a fellow male bust a nut, and knowing how satisfied they must be feeling in that moment.