No one should be a utilitarian. But from a utilitarian point of view, Batman's logic is superficially appealing: He can sacrifice one life to save 7 billion humans with 1% probability, for a net expectational gain of 69,999,999 lives. Until, of course, you pause and reflect. Consider the following utilitarian counter-arguments, in ascending order of quality.
1. Out-of-pocket cost.
Destroying Superman will burn immense resources, and utilitarians have to take these into account. But if you do the math, this is a pretty weak objection: Even if it costs $7B - a hefty sum even for billionaire Bruce Wayne - standard value of life calculations say that's worth 1000 lives, leaving a net benefit of 69,998,999 lives.
2. Opportunity cost.
Superman doesn't just have the power to destroy the world; he also has the power to save it. If there's a 1.1% chance that Superman will one day save the world if Batman lets him live, that amply justifies living with a 1% risk that he'll one day destroy the the world. And given the hazards of the DC Universe, the world is clearly safer with Superman than without him.
3. The self-fulfilling prophesy.
Batman's colossal error, though, is to fail to ask the question, "What would ever lead a superhuman as nice as Superman to destroy mankind?" And the most credible answer is: "If mankind tries to destroy Superman first." Batman makes the classic hawk's error: Failing to consider the possibility that he's making enemies with his aggressive actions. And when your putative enemy is Superman, that's an error of cosmic proportions. The common-sense strategy, rather, is to bend over backward to keep Superman on humanity's side.