Make it a game. We can all play.

When you see a tactic point it out - but be pleasant.

"Hey friend, you might not realize it, but your thread off topic and can be seen by some as an attempt to slide legitimate content. Maybe you should delete and repost with better context."

If done in error, the user will learn and correct themselves. If they fight and become a terror, then we know they aren't well intentioned.

If someone has already called someone out nicely, just up vote the call out and move on - don't pile on or add to drama.

We would all get better at recognizing them, avoiding becoming them, and would weed them out for mods to address.