Now, while I agree that people who are out to murder will find a way to do so either way, but it's exponentially easier to kill somebody with a gun than with a knife or baseball bat. Consider the problem of children getting shot due to accidental discharge: A baseball bat can't accidentally kill someone - you pretty well have to do that on purpose. In the case of a kitchen knife, there are two differences between them and guns (aside from the obviousness of it being a close range weapon): 1. people use kitchen knives every day, so children are accustomed to them and know how very dangerous they are because they're constantly reminded, and 2. knives are usually kept out in the open, and are used to cut food, so they lack the "cool and secretive" aspect that guns have, which is likely one of the main reasons a 7 year old would even be interested in a gun.
Arguing against gun control because it won't prevent ALL violence is ridiculous. It's like arguing against seatbelts because "some people will still die in car accidents".