Hessian, the Great Houses had their fair share of advanced tech at the time, and no indication that they would be incapable of producing it, or losing it in the future. New Dallas was a tough nut to crack on the way to more important Hegemony worlds, but threatening enough you simply couldn't or wouldn't want to bypass. Plus there's that whole Member-State superiority complex...
Nuking it seemed appropriate at the time.
