I imagine there's an acceptable amount of risk from playing sports. In hockey, it seems to always come down to whether something is considered a "hockey play". Smacking a guy in the head with a stick? Not a hockey play. Attacking a guy from behind? Not a hockey play. Throwing your leg up in the air and making a distinct kicking motion during a hit? Probably not a hockey play.
The only difference I see between this and the other neck/skate injuries I've seen is the additional kicking motion. It seems unnatural if it's there to preserve balance or prepare of ice impact. That video alone shouldn't be enough to convict anyone of unintentional homicide, but if this guy has a track record of sticking his legs out and even said something on the bench prior to the hit, it won't look good.