He could've literally thrown a rock or pipe or something at her. He's been shown to be able to be pretty accurate with his power. He could've just as easily grabbed StormFront with it and let Kimiko go crazy.
I see where you're coming from, but I feel you're being slightly pedantic. Little details like that would only bother me if the story being told made no sense. They were fighting a member of the seven, we've seen and been told time and time again how scary they are and impossible to fight and we've seen in the first 5 minutes that these "super-villains" are no real threat to the seven. The point of that scene was to show that Stormfront is a racist sadist, have the brother be killed by Stormfront (which she was going to do either way) which would give Kimiko motivation to wanna hunt the seven. I mean, would a lead pipe really stop that?