He wasn't booed for not singing in spanish - the crowd was noisey and he asked them to quite down a bit - someone in the audience yelled out "tell them in spanish" - which is when he replied "I don't speak spanish, I'm an American" - then left the stage. That aside, it's another media generated bullshit witchunt - they know that anything they can twist to sound like 'racism' will get a lot of clicks / likes and comments.