If we are going to chastise Trump for norm violations, shouldn't we first establish how normal or abnormal his actions in a given area really are? If we are going to say he is guilty of doing the unprecedented, shouldn't we look to see if there are in fact any precedents?
These "what about" questions also impose some accountability on Trump critics. When asked in good faith, they can be used to determine consistency and avoid double standards.
Nothing Trump does wrong can be excused by pointing to the Clintons or others. We don't want bad precedents to be set by the president or followed by future ones. What we should want is for all politicians to abide by the same set of rules — whether we like them or not.