I think there is a very thin line between confidence and arrogance though. And I’d say that it is people with a lot of confidence that tend to get arrogant. Too much confidence inflates people’s egos sometimes and they end up developing a god complex.
A doctor performing brain surgery, operating on a young girl to save her life, needs to be incredibly confident in what he's doing. Is he arrogant?
A fireman entering a burning building to save a trapped family from burning to death needs to be confident in his ability and training. Is he arrogant?
Just a few examples.
I totally disagree with you, there isn't a thin line between incidence and arrogance at all, they're two different things entirely.