Giordano Bruno

https://barryhisblog.blogspot.com/p/giordano-bruno.html

I came upon his monument by chance when visiting Rome in 2012. I knew of him, but I didn't know that there was a monument to him and where it was. The surprise discovery had a profound emotional effect on me. I sat at the foot of the monument and cried, and cried. 

He was a Dominican friar. To humiliate him, they stripped him naked, hung him upside-down and burned him alive at the stake, on this spot.

There is discussion about whether his crimes were disagreeing with the church on theological matters, or whether it was his astonishingly prescient scientific ideas. Whether it was one or the other or both, it was the fact that he vocally questioned and criticised established dogma. Full details at the link- https://en.wikipedia.org/wiki/Giordano_Bruno