I think you may want to go back and re-read the action descriptions in red and the elaborations below.

Werewolves can kill Van Helsing by simply electing to night kill. Van Helsing is only invulnerable to conversion, not to being killed outright.

If Van Helsing holds up in the bar for protection from night kills, he is is incapable of exercising his night powers. If a werewolf is also in the bar, Van Helsing has a 1 in N-1 chance of dying, where N is the total number of players being protected (including the Barkeep). If it's only Van Helsing, the Barkeep and a werewolf, he has a 50% chance of being killed.