The play is quite explicit in showing that Tyler Perry represents the heteronormative patriarchy of Black pop culture and that his Gospel Plays have had a negative impact on Usher's psyche.
Making fun of Sondheim wouldn't be remotely the same thing as critiquing Perry, though if he had made fun of Sondheim, the show might have run longer, because it would have given the White audience an easily recognizable target. I don't think most White folks actually know anything about Tyler Perry aside from Madea.
