If you destroy a window, then you're giving work to the person to replace it, but it means the owner of said broken window is out of pocket, which could have been used to buy something else and thus stimulate the economy elsewhere.
You're not talking about the proposal at hand at all. The bridges aren't owned by anyone who has a limited 'budget', but by the State.
Rather than building replacement bridges, wouldn't it advance the goals of the State more for them to use their printed money to hire and arm some more jack-booted thugs to go out and arrest people and put them in prison until bridges stop being blown up? Your proposal leaves us with fewer bridges and more police, which is hardly a desirable combination.
