

Find some place… as an example, hexbear’s instance has c/slop… to drop a link to the offending user’s comment or post and whatever happens… happens.
You’ve got the option of Reporting the post/comment to the moderators. Which will require you knowing the moderation rules of the community in question to take advantage of.
Short bullet point/talking point responses. Replies with things like, “This is racist/sexist/genocide denial/etc”, then disengage. You don’t need to get into a long drawn out comment war/debat bro situation.
Make fun of them for being a goober.
If you live long enough and interact with the world at large, you will eventually be a victim. You might have avoided 99 other scams or situations where somebody was trying to manipulate you but eventually, you’ll fall “victim” to something.
Having a duty to try to keep yourself from being taken advantage of, doesn’t mean that you should be denied help when you finally do get taken advantage of and that help be given without judgment.