"You're judging me!"

"That is correct, honey," isn't a bad answer, in light of the fact that the parent is supposed to judge her kid.

You asked, "What is the kid going to say then?" as if that answer will completely silence the kid? No way. An argument is going to follow. I have no right to judge me, or I don't want you to, or you're harming my self-esteem, blah blah. The mom comes back with, "Judging you is my job" and then ensues an hour of table-pounding from which no winner emerges, just a lot of hurt feelings.

When people tell me I'm judging them, I ask, "Wait a second, are you saying it's wrong to judge?"

They haven't learnt to be suspicious of my sneaky questions so they often bluster, "OF COURSE IT'S WRONG!" setting me up to win in two moves.

"Let me get this straight, you're making the assessment that it's wrong to judge?"

Yes, always wrong to judge. (I know they'll say ALWAYS and mean it to the bottom of their hearts because they have been so thoroughly drilled in this judgement by their teachers, their peers, their parents, and especially by their society in general, even to the point of having Jesus's words quoted to them: Judge not, lest you be judged.)

Then simply point out to them that they're judging. In making the critique and assessing it to be right, they've made a judgement, voiding out the statement that it's wrong to judge and that judging is always wrong.

Now you can move ahead and actually communicate with one another.