Good god, so many of us would have a deep existential crisis on our hands if the "Beach Boys" played Trump's inauguration.
Really? Then I think a lot of people here need professional help, or at least some relaxation with loved ones, with nature, with music. It really doesn't matter in the slightest whether this hypothetical show occurs. Just because I think he's by far the worst candidate ever elected, that has nothing to do with the sound of the band's music, even if some of the band almost certainly likes him. If something helps or hurts their reputation, that also has no effect on the sound of their music. They've been popular and unpopular dozens of times before. In the long run, this would be irrelevant. (Hell, in the short run, this would be irrelevant.)