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.
Also im not killing him. Just firing him. Find a new job and don’t do shit like that again.