I agree with everyone else that the BEST course is to continue to ignore.
However ... I've been through online dating and gotten so many replies, all over the map. And sometimes, even when I knew I shouldn't, I would let myself write a reply with more or less what I thought of the person.
Sometimes, even us careful and considerate souls are driven right to the edge by the 14th "ur hott but boring! wanna watch me flex?" type message, and I admit to replying with some bitterly sarcastic quips or even wordy and potentially-but-not-actually helpful things (given their unwillingness to self-reflect), sometimes.
Often, I would just delete before clicking "send," because the release was in the writing, but once in a while, when I wrote something constructive, I would just send it. And ... generally their response is no response, or an even more desperate plea for some, ahem, private time.
So, take it from someone who's tried it. It's not worth it. But it might help you slog through till you get to the gems (and yes, I did ultimately meet my husband on a dating site).