Why is it that you have to justify or make some excuse or blame so-called armchair musicians for what was a subpar performance? I'm a fan of Scott, too, and I frankly had hoped for a better performance, but I can admit it when my favorite artists aren't "on", and he wasn't. I watched it with other people who didn't even know who he was and every one of them thought he did a bad job.
It has nothing to do with being armchair musicians or artists. If it sounded bad to some people, it sounded bad. The man is not perfect; no artist is. Take off the rose-colored glasses for a change.