The obvious conclusion that Mr Penny did not have to kill Mr Neely comes from a combination of humane thinking and common sense. Most people view that as an example of healthy clear thinking. The views that
1) Mr Penny had no choice but to kill Mr Neely,
2) Mr Penny did nothing wrong
3) Mr Neely deserved to die, or
4) Mr Neely is responsible for his death,
are morally indefensible in civil society.
And you once again seem to be ignoring
5) Mr. Neely appeared to be a threat to those around him such that Mr. Penny felt it appriopriate to intervene, and Mr. Penny unintentionally overdid it
Which seems like it should be defensible, at least to me.
Assuming Mr Neely was a threat to those around him (a big assumption), why should “ aw shucks, I overdid it” be an acceptable excuse for killing someone?
Chokeholds are tricky - if you don’t know what you are doing, you shouldn’t use it.
Unlike Mr Neely, Mr Penny will get a chance to defend himself in court.