You are delusional My Friend.
Neely threatened to kill the people on that train.
For all Penny knew, he had a gun and was going to use it.
Neely struggled until he was unconscious. Was he trying to reach a weapon? You have to assume in the moment that he is.
We Neely loses consciousness, Penny then released the pressure on Neely's neck...you hear the guy in the video say "he's not squeezing anymore".
And then he is released and placed in the recovery position.
There were SEVERAL placed where Neely could have 'tapped out'. Had he stopped struggling and said "ok, ok" the pressure would have eased and they would have waited for the police.
Your problem is, you live in a fantasy world where you just assume the guy who threatened to kill everyone doesn't have a knife, or a gun...surely he doesn't mean it...and you just hope for the best. Just let him go. It will be fine.