I am not saying that people have to like BYU or not--he can hate BYU for all I care. However, when I go to sacrament meeting, I am there to take the sacrament, feel the spirit, learn of Christ and to be edified by those that speak.
For a missionary (or any member for that matter) to get up and bad mouth any school, let alone Brigham Young University, it is completely inappropriate. The church pulpit is not the right place for anyone to to disparage anything or anyone.