Agree to disagree. IMHO, there are more people who thrive on internet conflict than thrive on being ignored.
It takes self control, but walking past the problem is sometimes the more effective solution.
"Man, that asshole on the Internet disagreed with me. I'm going to write a detailed rebuttal of why they're the asshole."
vs.
"Hunh, I wonder why I occasionally get down voted and no one ever responds to me? And also, the responses I do get are a lot nicer in tone than mine..."
You’re right that there is a challenge about giving attention when that’s what they’re seeking. I generally prefer either flagging (worse cases) or up-voting the one person who left a “dude, not cool” reply so they get clear community feedback.