So ultimately both sides are right in their own ways. It's not necessary for your survival to be shooting through the fence since its impenetrable by a knife, a humans focus should be on the hole in said fence because that's the only way for Z's to reach you. But the argument can be made to shoot them through the fence to prevent a bhopper from flying in; since zombies should always be actively trying to infect the humans if they walk into the room, it can be said they are coming after you. But since everyone's worried about points we have come this this weird middle ground of humans trying to rack up a nice Z kill streak and the zombies doing nothing because they dont want to inflate the humans points and ego any larger then they already are.
Sorry if I don't make sense. I'm not too great at putting my words to thought, but like it has already been said just remove the fence and this issue doesn't come up.