Ignoring the evil of Arpaio, and just commenting on the pardon.

To critique a Harvard professor is easy.  Just read the sentence in article two of the Constitution and it has No limitations on the pardon other than excluding it from impeachment pardons.  I Taught the Constitution for 30 years in public schools so I have reread it many times and have a pretty good idea of what it says.  How it is applied is the job of harvard educated lawyers and other legal minds to find ways to twist the words and meanings to reflect the needs of their paying clients.
It is the duty of citizens in a republic to inform themselves and not just rely on what those in authority decide to tell them.  Some things are subject to interpretations, but pardon power is black and white.