So far, for the people that like metal (myself and a large handful of others on this board), having these bands play has been good. The problem comes up the first time they have a rap act perform. trust me, as this thing goes on, it will happen.
It will piss me off and make me less likely to get a show if I am on the fence about it already.
If the acts are playing for free (not likely) or as fulfilling a sponsored obligation (probably the case) then other than disliking the music, no one should really complain. If they are taking money for these appearances, that is a crime to the undercard fighters that could use an extra $10000.
On a side note...Metal Sanaz is unbelievably hot. She is definitely not for everyone, but sign me up!