Is it aimed at you personally, or deliberately over the top?
Behaviour like this is sometimes called
Attacking the person rather than answering their argument, so the reply becomes self-defence and the argument is quietly dropped.
Deliberately absurd, provocative or offensive posting, which at volume or at the wrong moment degrades a discussion without engaging with it.
What would tell them apart
Something aimed at you personally attacks who you are, so replying becomes about defending yourself rather than making a point — take the insult away and there's no argument left underneath it. Absurd or deliberately offensive content posted into a space is usually not aimed at anyone in particular; it would read the same whoever happened to be there, and its target is the space rather than a person.
Why it might be none of these
Two different innocent readings sit under this one, because the two shapes above are not alike. Asking whether someone is actually in a position to know something — their credentials, their conflicts of interest, whether they were there at all — is a legitimate question about how reliable a claim is, and only becomes something else when it replaces any engagement with what they said. Separately, communities run on absurdity, and a thread full of nonsense is very often just people enjoying themselves; what matters there is whether it is displacing a conversation somebody was trying to have.
None of this covers stalking, doxxing, swatting or harassment campaigns. If any of that is closer to what you're facing, go straight to Red lines instead — the advice on this page was not written for it.