The fans that Eminem choose to give the middle finger to will likely take their viewership and funds elsewhere, and rightfully so. One way or the other, entertainers need to learn that their fans are what makes them great successes. Alienating those who support you due to political differences is the ultimate form of career suicide.
Moreover, Eminem is in absolutely no position whatsoever to claim the moral high ground. He is infamous for his derogatory lyrics where he promotes violence against women and gay people. Hopefully, the short term glory of millions of views and heavy media coverage was worth it for Marshall Mathers.
This is truly the beginning of the end for his career, and like all cases of self sabotage, Eminem did it to himself.