I think if anybody's to be commended for their principle it's probably the organisers? They have their dress code, he violated it, was warned, continued to violate it, and they enforced the rule despite his name.
I think they come off better, personally. I'm not saying that should be the dress code, he shouldn't be allowed to wear jeans or whatever, or even that it's bad of him to decide not to play rather than to play in jeans. I just don't think 'it became a matter of principle' is a great argument for him, because it just makes me think better of the organisers for similarly standing by theirs.