"We" decided that Tuskegee was bad enough that it should be stopped before harm is done, and that there is no appropriate or sufficient "punish[ment] in retrospect" for the fallout.
The government makes you get a license to drive at all, then "drive a Pinto" versus "drive a Trabant" are similar enough that they don't require more info. They require you to get different licensure to drive a bigger truck where you could potentially cause more harm, or to drive an airplane. In this analogy the IRB is the DMV/FAA/whatever, and you're asking for permission to drive a tank, a motorized unicycle, a helicopter, an 18-wheeler or a stealth fighter. You don't get a Science License rubber stamp because that's like getting a Vehicle License - the variation in "Vehicle" is big enough that each type needs review.