he isn't "becoming like rick" he's becoming something different altogether, something far, far worse.
rick hasn't done something this terrible and undeserved in any episode, and claimed it was a just punishment.
rick is apathetic when he hurts people, morty has always been vindictive, or even malevolent
for rick it is enough to eliminate an unwanted person for personal gain, but morty wants to cause a man to suffer for the rest of his life for the sole sake of it.
you can see it best in the past 2 episodes, rick says "why would I care if someone who tries to kill me gets away with it, 20 people try to kill me every day."
morty starts hushing him like a serial killer, and horribly disfigured him for imaginary transgressions.