While I agree with @Mick, at least up to a point, @HotLicks makes a good point. You seem to be asking about the phenomenon of attempting to deflect criticism for saying something stupid by deliberately saying something even more stupid.
In a general sense, such behavior is a form of defensiveness by which a person attempts to deflect criticism and/or minimize the embarrassment of having just said something ill-advised. After being excoriated by someone who seems to know what they're talking about, the defensive person tries to weasel out of having just said something stupid by deliberately saying something even more stupid--stupid to the point of being patently ridiculous.
In other words, such a ploy is an attempt to weasel out of having just said something ill advised.
Such behavior could be called any number of things, including
an attempt to save face
an ad hoc attempt to minimize embarrassment
an effort to rationalize having said something stupid
a desperate move to persuade a person you weren't serious about your former comment
twisted logic: an obviously stupid comment which has been proved to be stupid will somehow lose its taint when followed by an even more-stupid comment
A social psychologist would probably have a better handle on this phenomenon. The defensiveness I mentioned could be triggered by a commonly used term in social psychology: cognitive dissonance. Put differently, a person who has just been exposed as having said something stupid feels conflicted--dissonant, because on the one hand they perceive themselves as being quite bright, but on the other hand they've just been exposed as being not so bright.
It's as if the person's self-talk goes as follows:
"Well, which is it: bright or not so bright? I still think I'm bright, so to get rid of the dissonance I'm currently feeling I'll attempt to appear bright by saying something even more outrageous in hopes that my interlocutor will think I was just kidding when I made my first comment."