ubiquitin,
“do you think adultery should be ilegal?”
Absolutely. If the government is going to be involved in regulating marriage, than it has a responsibility to protect the rights of the spouses. Inasmuch as marriage is a contractual agreement that includes fidelity, there should be consequences for breach of contract. But even beyond that, adultery can cause psychological and even physical damage. To do that to another person should certainly be illegal. And note that I haven’t yet appealed to religion.