I thought it was rather clear....but let me just offer a verse first
Act 5:28 Saying, Did not we straitly command you that ye should not teach in this name? and, behold, ye have filled Jerusalem with your doctrine, and intend to bring this man's blood upon us.
Act 5:29 Then Peter and the other apostles answered and said, We ought to obey God rather than men.
The point being that
either it was obedience to man or God in luring Servetus to Geneva, digging up the evidence against him, turning him over to the authorities, being the chief prosecutor or it was obedience to man.
Same goes for the other Christians that were complicit in this. Who should they have obeyed? God or man? IF you say man then either you approve of disobdience to God OR you approve of putting a man to death in the worse possible way (burning alive) for having a doctrine not sanctioned by the state.
The point is, if it is wrong to put a man to death for heresy the those Christians chose to obey man rather than God.