Why would they do so?
You seem to fail to understand any of the history you read, nor are you capable of placing it into a context. Let me try somethign contemporary. When you see "heretic" think "Muslim fanatic." Not "quiet, unassuming schoolmarm."
That might help you to understand why heresy, in certain historical circumstances was considered a capital offense.
Or it might not. I can't make a horse drink.
SD
That may help you to understand why I don't trust you to define heresy.