As-is, trying to save a survivor who is being grabbed with melee is impractical. Each character's body gets in the way and you wind up swinging at air more often than not. You're much better off trying to line up a shot, and even that isn't too practical and shouldn't have to be your first choice. By making players able to swing though one another in a crisis, teamwork goes up, people can more easily watch each other's back without relying on firearm, and staying quiet is more viable. That last bit is important because if you're already down and out the last thing you need is to bring more trouble because you were trying to save a friend. Or worse-- letting them die because it was to the benefit of the team and your character doesn't know how to swing at the biter and not the bite-ee.