Sensor Scott opposes the blanket ban because insider trading is already illegal, and thus the ban makes punishable otherwise entirely legal behavior. And he's right- it isn't, and shouldn't be, illegal or considered wrong to be successful, if done the right way.
There's a middle ground somewhere in there I'm sure, but given how suspiciously well some members of Congress have done, and how there's been seemingly not enough accountability of it, I'm not terribly empathetic.