Let’s say one of the partners is out of town and the other decides to have sex with a random person from Tinder for one night. There’s no follow up meeting between the two, it’s just one night. I don’t really see why this is a big deal. I do in fact disagree with cheating one someone and clandestinely being in two relationships, since that shows a broader personality of dishonesty and being bad at communicating. Cheating is described as being bad because it’s a breach of trust, and because one person in the relationship isn’t devoting themselves completely to the other. But I think it’s still possible to devote yourself wholly to a person you love whilst occasionally having sex with other people. I think society should be less monogamous in general.