I had a Captain Know It All Doctor, too.
When I was 11 I broke my leg. I spent several weeks in hospital, then they let me out with a (hip to toe) lightweight cast. Said cast was made mostly of some form of fibreglass, which, it turns out, I am highly sensitive to. (that's not the know it all part. We didn't know, there's no way the hospital could have known)
However, when my parents took me back to say "there's something seriously wrong, you need to take the cast off and find out what it is" the consultant was beyond patronising. He ignored the fact that my GP had referred me back as he was concerned, and my parents explanation that I was a very stoical child and if said it hurt, I did not
mean it itched. In the end, my mother told him she was not leaving until he took the cast off.
He actually said to my mother (and I Quote) "You and your daughter are making a fuss about nothing. I will take it off, as you insist, but you needed think we will re-plaster the leg afterwards, when you see it's fine. "
He never apologised afterwards, when (very slowly, (and painfully for me)) they removed the cast and found that yes, actually, it was a very long way from fine.
Years later I saw a letter he'd sent to my GP which actually *said* he'd thought that we were making a fuss about nothing, and was surprised to find that there was a 'serious reaction'. Never bothered to admit that to me or my poor mother. It's more than 20 years ago, now, and *still* annoys me when I think about it :-)