You could not be more correct. Let their heads explode - it is like the smell of napalm early in the morning!!!
In the United States, the pardon power for federal crimes is granted to the President of the United States under Article II, Section 2 of the United States Constitution which states that the President "shall have power to grant reprieves and pardons for offenses against the United States, except in cases of impeachment". The U.S. Supreme Court has interpreted this language to include the power to grant pardons, conditional pardons, commutations of sentence, conditional commutations of sentence, remissions of fines and forfeitures, respites, and amnesties.
The President doesn't have to justify or explain his pardons to anyone, including the news media, pundits, editors, reporters, ex-campaign managers, lawyers, ex-perts or democrats in Congress.
If they don't like his pardons, they can run against or vote against him in November, 2020.
Other than THAT, they simply have no call in the matter.