Well, given that a Runt is prone to violent rages but can't transform completely, it is possible that they aren't really a threat to other werewolves, who get a good deal bigger and stronger in their transformed state. In which case it'd be more of a concern for werewolves too young to defend themselves or outsiders combined with a bad response to extremely damaged children. There may be cause for werewolves that don't eliminate their Runts to try and record how they dealt with them.

Also, the werewolves seen here are stupid college kids. They're going to think about sex before race.