bespangeled
Scooby
A great many things are more dangerous than kissing (or sex for that matter), and yet people tend to regard cheating in romantic relationship as more of a betrayal than most of those things. And in any event, strictly kissing also can transmit diseases, you know. For all we know, vampire blood and teeth might be sterile because magic. 🙂 IIRC, nobody in the show raised any infection related objection to the infamous suck jobs, I don't see why we should. It was a very transparent and silly device for sending Riley away I doubt the writers spent any time thinking on its possible implications or interpretation other than the clumsy cheating metaphor. The very notion of vampires offering suck jobs for money and being tolerated the Council and previous Slayers is preposterous.
The disease idea was a metaphor for the chance that Riley could get turned. Hell, half the vamp population has to know who he is and that he's with the slayer. Whether or not it's mentioned specifically the risk is there.
As for the rest - Riley become a selfish needy little high maintenance whiny bitch boy at this stage of the game. The entire conversation is disgusting - blaming Buffy because she won't change into his ideal for a woman, and then claiming he is the victim of intolerable pain because she's too busy to cater to his needs.