Comment by geofft

That's all good in theory, but there have been demonstrated attacks against man-in-the-middle-able protocols and we've lacked the ability to respond usefully, precisely because the protocols were designed to be man-in-the-middle-able. Everyone knows it's happening and it's even easier to detect than your example, but there's nothing useful to do with that knowledge other than complain.

https://www.eff.org/deeplinks/2014/11/starttls-downgrade-att...