Kevin Williamson:

The point of keeping Trump administration veterans out of positions of public trust is not to punish them — it is to keep them out of positions of public trust. We should do that because the public cannot trust them. We have norms, institutions, and procedures designed to protect the public trust from those who would abuse it or who, having been invested with some great authority, neglect that trust in the pursuit of private gains, be those financial or political. These are useful social tools, and we should use them. 

Clearly, concisely, and convincingly put.