Side note: the parent's entire argument boils down to this:
"Look at how hurt the teacher would be by being fired, you are a bad person for suggesting that.
Setting aside the Ad-Hominems¹ like "Are you better than the teacher"?, this is a textbook example of the logical fallacy known as Appeal to Emotion².
Which is delightfully ironic given the numerous people accusing you of being overly emotional in the point you're making that a teacher who willfully breached trust and abused their authority over children shouldn't have such authority.
This says much more about the people criticizing you than they realize.
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Also im not killing him. Just firing him. Find a new job and don’t do shit like that again.