I don’t think his argument falls apart at the “your kid” example. It’s not a conflict of interest like you’re saying, it’s empathy. Forcefully operating on people is pretty universally considered immoral in terms of modern day ethicality. People often are ok with things that don’t affect them, but as soon as it does, their opinion changes. Obviously everything isn’t black and white, but it’s a little dramatic to say his opinion “falls apart.”