As for me, I love to hear constructive criticism from my readers, so I always do ask them to comment. It's never been a problem to me as these were one way for me to learn. I'm not saying I don't have feelings as I am also human.
But it doesn't mean you should start critiquing someone else's post just because you don't like it. If you are that person who are thick skinned about things, well, not all people are like you. There are few cases I have seen where people seems to demolish other people's work but this is distinctly very unpleasant way.
If people would voluntarily ask you for critique, just make sure it is constructive and polite. Move on if you were not able to do that.
This were once part of my experiences when I was first started. Many people comment destructively on my works. But later on I just learned how to deal those critique until such time I started to stop being bothered by them. If you really learned to deal with such, you will also learn how to give critiques the constructive way, and in the most polite manner.