I've seen various articles about people making such comments about the Thompson murder on social media, but I guess I'm not sure if I believe that they really mean it, or they're just being flippant. If they do mean it, that's pretty scary.

As for Penny, from the little I've read about the case, I don't think that he's a murderer, nor that he should've been sentenced to a long prison sentence necessarily, but the 'criminally negligent homicide' charge does seem to fit. Intervening and restraining Neely when he threatened other passengers may have been an act of good citizenship, but when Penny kept up the chokehold for several minutes, he should've known there was a risk of causing serious injury or even death.