I find it really strange that so many people will happily eat a guy's cum, but freak out at his spit. From an objective perspective, one would expect cum to be perceived as more disgusting. It contains more live bacteria per cubic centimetre than spit, plus a few millions of live human cells. It also has a pungent taste, whereas spit literally tastes like nothing at all.
Even mor baffling is the fact that you ingest a guy's spit anyway when you kiss him, so it's not as if you haven't already eaten spit before. So, when his spit-covered tongue roams around inside your mouth, it's fine and dandy, but if an equivalent amount of spit gets into your mouth on its own, it's suddenly gross and unacceptable for some reason.
As for the opposing camp, most of them are equally baffling to me. Most of you spit lovers are eager to swallow a guy's spit, but when he expects you to return the favour and spit in his mouth, you suddenly become paralysed. Why is it that 90% of those who are into spit, only want to receive, and refuse to spit in another guy's mouth, while the other 10% only want to do the opposite? Why is it so nearly impossible to find someone who is willing to both give and receive?