Sign of a weak player
You should not worry too much about these kinds of reactions. Most of the time they indicate an unexperienced poker player who can't exploit his opponents by playing in a strategical manner, instead they use a very poor approach trying to intimidate, which is something everybody can do it with no poker skill whatsoever. What should really concern you when facing these players is how much is that bothering you? Because, in my oppinion, a good poker player makes good decisions when having a clear state of mind. So, my advice here would be to focus most on what's really happening at the table than in the chatbox. Good luck!