"To Spare Servetus............"

Why did John Calvin have Michael Servetus martyred......burned at the stake?  Because Servetus did not believe in the trinity, and he spoke against it.  Calvin had written a booklet in defense of the trinity.  Because Servetus spoke against it, Calvin argued "that to spare Servetus would endanger the souls of many."  A Christian scholar by the name of Sebastian Castelio wrote an essay entitled "Contra Libellum Calvini," (Against Calvin's booklet).  Here is part of what he wrote, and I agree one-hundred per-cent:  "To kill a man is not to protect a doctrine; but to kill a man.  When the Genevans killed Servetus, they did not defend a doctrine; they but killed a man.  If Servetus had wished to kill Calvin, the Magistrate would have properly defended Calvin.  But when Servetus fought with reasons and writings, he should have been repulsed by reasons and writings."