The guy who shoved him was backing up and turning away. That doesn't fit the description of reasonable fear for his life. That's why he was rightfully convicted and sentenced.
You call out someone for bad behavior, like parking in a handicapped space, you are operating on the assumption that they are civilized enough, that such a statement will not immediately escalate into violence.
Do you support the idea that, as a society, that people can complain to other people, without it immediately escalating to violence?