In my experience, when people say "don't judge me", they are generally acknowledging that the person they are telling something to probably won't agree with their actions. And actually, when I have heard it, the person is asking for some sort of help in sorting something out. The Word isn't saying don't have opinions, nor ignore what is wrong or right - it's saying we all sin and are still redeemable. Like Rav is saying - if you are just trash talking someone down - condemning - what does that accomplish?