Rocks can kill people.They can go through car windows.If I,a juror,was shown convincing evidence that rocks were being thrown at him *before* he accelerated I'd be strongly inclined to vote "not guilty".
If rock throwing was a legitimate factor in this incident it comes to resemble Trayvon Martin IMO.
We know that antifa had bats and clubs that seem to be everywhere. they were wacking his car right after the accident and before he reversed up the street. The police reported that he was frightened when they picked him up.