So he didn't hit all the notes.   He hit the vast majority of them, sang with spirit, ended strong, has great stage presence, no nervousness at all.   Very impressive for anybody in that context, let alone someone so young.

More power to him.

I preferred his version to that of Jimi Hendrix, for instance--(if this be treason to "folk" or "our music" make the most of it). He didn't feel he had to bend the melody til it was barely recognizable.

After all, it's a great drinking song (though the original words are weird)--and probably a great test of whether you've had too much (if so, you probably have a really hard time hitting the notes, which are a challenge even stone sober).

I'm sure the racists, among other things, are bitter that their ethnic groups are becoming a minority in the US.