I think you are right. President Trump should treat this stuff like the third rail on a subway.
My son is a conservative Trump supporter. However, he is concerned about the idea of prosecuting Hillary or Obama simply because it looks like political retribution. The MSM will play on these concerns if it looks like President Trump is leading the charge.
On the other hand, if it looks like loyal elements of the FBI, DOJ, and other agencies are forcing the hand of the DOJ to pursue charges against these folks, then it looks a lot better.
I think we should all be concerned about how this looks to our allies. If it appears politically motivated, then it will be a stain against America. But if it is limited to miscreants in the Democrat Party, we have a chance of making it look like localized corruption.
Given the venue; i.e. D.C., it might be quite difficult to get actual convictions. The politics needs to be totally in the background so that Joe Blow public realizes that, if the resulting trials do not result in convictions, then THAT was due to politics.
A good result would be if at least a small number of the underlings can be induced to turn state's evidence. Then, the appearance of innocence will be stripped from the upper layers; e.g. Comey.
There will be a weasel like John Dean ...there always is.