I think it is valid to kill the patriarch with pipe bombs because:
1) It is really funny to lure him to a part of the map with the bombs. It is not that easy to lure him to the right place. Sometimes it requires locking some doors, sometimes it takes making people look for him and then run for it...
2) It requires some teamwork to be done, people using their money to buy pipe bombs, put them in the right place before the trader countdown ends.
3) It fails many times. Sometimes the number of bombs is not enough, sometimes the pat does not get all the damaged and survives, sometimes he just lauch the rocket laucher at someone in the wrong place and the explosion detonates all the pipe bombs. When it fails, all the team must quickly of a second plan.
4) It is really fun to be done. I think those who want to kill the pat at another style will do it just for the fun. If someone does not like to kill the pat using pipe bombs, then he/she just wont do it. This game is all about style, some players are all proud to be the better killers, some players want to be smart and lock doors, some players love to boss other players around, other players love to heal and help their companions, all of them are rewarded for being themselves.
5) Killing the pat is never easy, it requires luck, right circunstances and people being at the right place and the right time. There was a time when my team was placing pipe bombs at pyramid map to lure the pat. Unfortunatly most team members was near the bombs when he appeared, and the pat just launch a rocket at us exploding the bombs and everyone.