People who are ruthlessly cruel to strangers on the Internet are, IMHO, driven by lesser extremes of the same deficiencies of character that make people terrorists. So he didn't crash a plane into your house. He took enough glee in attacking just as viciously with words. By doing so, he gives up his own dignity and any basis by which any intelligent person could take him seriously.

As for his points, there are seeds of truth in them that are twisted into lies and logical fallacies, but I can't be bothered to take the whining of a pest like that seriously.