Debating on the internet is insane, because people never want to accept what you are actually talking about. They decided the topic long before you wrote your first message and they cannot be talked out of it.
@lina
Unironically, that does happen to be the easiest way, to see if they are there to talk or shout.
If I'm not sure, I write a single insult and continue with the argument. If they then refuse to engage on argument, and focus on insult, I know it was a waste of time.