One way to deal with guys like that is for the group to just let them go. When they get to the front, which they often do, the whole group just sits up and refuses to play. It's not always easy because everyone had their own agenda and goals for the ride but if the guy is a problematic as it sounds you sometimes have to work together with group passive aggressiveness and change the rules.
It sounds like that would be near impossible with this group so just try and stay away from him. I stopped doing weekly scheduled group rides some years ago for far less than you describe. I've really come to enjoying riding alone or with a small group of good friends.