You can't complain about what one side is doing, when you are doing the same thing on your side of the fence. If you do, all you demonstrate is that you are a hypocrite and should not be taken seriously, because of your biasness.
The problem is not him pardoning his son. All of them would do that with the power. The problem is constantly denying you will do it and having others, like your press secretary, state over and over again that you would not do it. If he would have just been honest and gave an answer of, "I will wait to see how this all pans out before I make a decision" he could not be called out on lying.