He was not sexist, you are simply using it as a weapon to gain moral superiority. You cannot be sexist when the persons gender is unknown, and he did not assume a gender, gender and sexism was not part of the conversation until you brought it up. 

3rd wave, as in 3rd wave feminism. 

He was attacking others because he felt attacked, by the comments people were using since he obviously identifies as part of that group. You laugh and make fun of other groups right up until someone attacks you, and then its immature, rude, sexist, etc.
congratulations "capturing his voice"? you have become exactly what you were decrying. 

People you dont agree with are people as well you know, and have the same rights that you do. For example, if we took your comment and replaced key words to apply to a different group a whole bunch of snowflakes would have been triggered.
"at the expense of that dim witted copper losing his car, lol." or 'at the expense of that dim witted woman losing her car, lol.'