The Honor Code is much more stringently enforced now than it was in the 70's and 80's when Lavell was coaching. It was easier to keep things quiet and handle disciplinary matters "in-house" and I'm sure there were also many honor code violations that the coaches never knew about.
Now with the proliferation of social media such as Twitter, Facebook, Instagram, etc, it's much harder to keep honor code violations secret or at least confidential and consequently it's also much easier for coaches to find out about them. Thus, they're more frequently prosecuted now.
I think a non-LDS player with McMahon's free-wheeling and rebellious attitude would have a very hard time adapting to and surviving the current atmosphere at BYU.