Note: Galileo wasn't executed. Rather, threatened with torture (though never actually tortured), and put under house arrest for the rest of his life.
And yeah, he had a problem with not being able to be diplomatic with people who were
wrong, dammit.

...and the powers that be had an even worse problem with not being able to just let such things go.
Edit: come to think of it, Gallillo's is probably one of the earliest historical instances of nerd-rage recorded. Though not the oldest -- Archimedes had him beat by a couple thousand years (and it got him killed).
And yeah, some ancient greek dude (Democratius?) actually came up with an amazingly accurate estimation of the cercumfri of the earth and moon, and a reasonably accurate estimate of how big and far away the sun was.