Heresy is any opposition to any "orthodox" belief. Some orthodox beliefs themselves are heresy. Even though that would be an oxymoron to the simple definition of orthodoxy. The only view that is "orthodox" is Scripture itself. Yet we have many claims of at least two branches of the church at odds with each other's "orthodox" views.
Heresy is not just being against a single view. The fact any church member was declared a heretic was based on not accepting the whole body of what was taught. It would be like breaking just the simplest OT law is breaking the whole Law. Those put to death as a heretic in the majority of examples were more saved than their accusers. Jesus pointed that out when He told them, "those without sin should cast the first stone".
Only those trying to maintain mental control over other individuals would put people to death. That is not how the redeemed operate. Obviously God has instilled even in wicked humans the will to live as long as possible in the flesh. Those without hope, have given up. Those who deem it necessary to kill other humans only do it out of selfish personal reasons. Definitely not because they are acting from God's direct orders.
The only time God gave His chosen people the order to kill every last human on earth, was to remove those wicked nations out of the Promised Land, so the nation of Israel would not follow after their wickedness. And then Israel still was not able to complete that order. It was not because those nations were part of Israel and started to introduce heretical doctrine. Sin was not supposed to take hold in Israel and those who broke the law were to be condemned to death.
The NT church was not to be in bondage of such a law of death. The heretics were to be removed from membership, but never was the death penalty ever instituted. If such a one broke the civil law, they were to be handed over to the civil authorities. The point is when a corrupt church becomes orthodox, even the truth can be deemed a heresy.
It is ironic when those who do not except free will, ask for people's free will opinion.