How should one respond if they hear 'wife gives my friend handjob stories'?

One should firmly oppose and ask the person sharing to stop. It's not something that should be talked about.

This is completely unethical. A marriage is based on loyalty and fidelity. Such behavior violates the trust within the marriage relationship and goes against basic moral principles.

Well, it's a really tough situation. You might need to seek some professional help like couples counseling. This can provide a neutral space where both of you can express your emotions and work towards a solution. Also, you need to decide if you can forgive and rebuild the relationship or if it's beyond repair.

One should firmly reject listening to or spreading such stories. If possible, tell the person spreading it that this is inappropriate and unethical behavior.

First of all, don't believe it immediately. Then, if it seems to be part of a malicious rumor - spreading campaign, you could report it to the relevant authorities if it's getting out of hand. We should not allow this kind of slanderous and unethical behavior to continue unchecked. Also, encourage others around you to have a more positive and respectful attitude towards others' privacy.

One should firmly condemn the sharing of such a story. Politely tell the person sharing it that it's inappropriate and private matter.

No, it is completely unethical. Such stories involve betrayal and inappropriate behavior that violate the basic principles of marriage and friendship. These are private and immoral matters that should not be shared.

Politely tell them that this is not an appropriate topic for discussion.

If you hear such stories, you should distance yourself from the source. You can also let the person know that this is not something that should be talked about as it is disrespectful and unethical.

Politely distance oneself from the situation and the person sharing it. Maybe change the topic if possible. There's no need to engage further as it's an inappropriate topic.