There must be some reading comprehension problems in this group. 

I'll break it down for you (again.)
a) He did not deserve to be attacked legally or morally.
b) He should have known (and probably did know) that he may be attacked, regardless,  because some members of the group he confronted are not as rational as we would wish them. 
c) This isn't that difficult to understand; people are often irrational and emotional. That is not an excuse, it's a fact of life.