What would you take irrational behaviour to mean

[Worriedmother666]

In a person

Doing something against logic or reason, perhaps impulsive. Being unwilling to listen to alternative pints of view or take a moment to consider.

Either a) as poster says above doing something impulsive, based on emotions and probably against the person’s best interests.

Or b) with my cynical hat on, having a perfectly normal upset reaction to a shitty, passive-aggressive person who delights in winding people up, then mocking their hurt.

It would depend who was describing who and the context behind it.