Elton John, Celine Dion, Bruno Mars, and Katy Perry are just a few of the artists that have refused to perform during the Inauguration Celebration next week on Washington, D.C.  No surprises there.  But Gene Simmons and Garth Brooks?  What are they worried about?  I can't picture any of their fans having voted for Hillary Clinton.  Here's who will be performing:  3 Doors Down, Toby Keith and--wait for it--Lee Greenwood (who's only there to sing his one hit, "God Bless The U.S.A.").  Since these guys are not exactly burning up the charts these days, they're probably not worried about any potential backlash.  As a matter of fact, they could use the exposure.