Doing a facial recognition, tying that face to a name, an address, an employer, broadcasting to as many people as possible about that person, going out of your way to contacting that person's employer, harassing them non-stop, chasing them out of any social media with mass reports, etc.
Except, if we compare your analogy to my argument, the person that cheated on his wife is the terrorist, he actually committed an act that is criminal. If the person uttering hate speech is to be created within your analogy, it would be a person that is saying ok with people cheating on their significant other. Until he actually do it, we shouldn't be outing them.
A black man was able to make people leave the KKK by befriending them.
A second source about the same guy.
People can change. We need to give a chance to those that have
yet to commit terrorism. Else we are just postponing a problem that can come back even worst.