I mostly agree, but would offer a friendly amendment. Given the imperfections in the law, prosecutors need some leeway to exercise their discretion about which cases are pursued balls to the wall and which are allowed to slide. I know that that is exactly the sort of thing that gets abused and gives an advantage to people with the right connections, but I think it is inevitable. The law is too blunt an instrument to be able to properly address all the different scenarios humans concoct. Sometimes the system relies on the good faith of those in charge.

Your basic point is dead on, though. Howard Baker exemplified the principle when he said that we needed to know what President Nixon knew and when he knew it. Other Watergate figures - Archibald Cox, Elliott Richardson, and William Ruckelshaus come to mind - also stood up for principle and are now well-regarded as a result. http://en.wikipedia.org/wiki/Saturday_Night_Massacre