Read other letters about this article
Different people have different bounderies when it comes to sexuality. Some people have anal sex on the first date. Some people won't even kiss until they've been dating a while. This includes definitions of cheating. Some people feel that flirting is cheating. Some people don't feel that making out is cheating. Some people have a good place for porn in their relationships. Some people feel that using porn is a type of infidelity.
People's bounderies need to be respected. Some people have stricter bounderies than other. If your partner is uncomfortable with a sexual act, then to continue with it is just wrong. People have limitations. Sometimes they can be talked out of them. Sometimes they can't. If you can't respect your partner's limits, its a real problem.