For own safety, from snapper to be if you do not leave, then disengage from contact with him. Or learn to defend their psychological space, without entering, however, argue with ignorant and not stooping to his level. For the art of insults he certainly much more experienced than you.
It is important to understand that when the snapper offends you, he has no claim to you personally - he decides to own psychological problems that are not to your personality in any way. Or almost nothing. Remember that you do not have to be responsible for someone else problems and bad mood.
Criticism, as already mentioned, concerns what you are doing or not doing. Moreover, constructive criticism must come from the mouth of someone who is competent in the area that this criticism concerns. Because its main purpose - to make your actions more effective and the results more significant. In contrast to the brutality with a view to diminish your self-esteem. This point is very important to understand.
Stop before reading rebuff criticism. Does this criticism or an insult? Think about what goals you have just heard the remark.
Perhaps it has valuable instructions on how to make your work more efficient. Or maybe, it contains an indication of the shortcomings of your work - the ones you do not notice, but that pull you down. Think about what benefits will fix their own mistakes, and thank criticism. After all, he had you a favor, and not trying to offend you.