I personally hate, HATE, when singers use the National Anthem to show off their talents instead of just sining the song - and some people who have sung the Anthem at BYU games have been truly awful - but I have no interest in tearing a person down who is living their dreams, doing their job, or trying their best. No good comes from it, but it has the potential to put bad stuff out there into the universe.
Of course, if you PAY $90 to see Tool, and you see them and they suck - gloves come off. But when it's free and you haven't paid anything for it...