I knew little about the guy so I googled him:
"Arpaio has been accused of
various types of
police misconduct, including abuse of power; misuse of funds; failure to investigate sex crimes; improper clearance of cases; unlawful enforcement of
immigration laws; and election law violations. A Federal court monitor was appointed to oversee his office's operations because of complaints of
racial profiling. The
U.S. Department of Justice concluded that Arpaio oversaw the worst pattern of racial profiling in U.S. history, and subsequently filed suit against him for unlawful discriminatory police conduct.
[10][11][12][13]
Over the course of his career Arpaio was the subject of several federal
civil rights lawsuits. In one case he was a defendant in a decade-long suit in which a federal court issued an
injunction barring him from conducting further "immigration round-ups".
[14] A federal court subsequently found that after the order was issued, Arpaio's office continued to detain "persons for further investigation without
reasonable suspicion that a crime has been or is being committed."
[14] In July 2017, he was convicted of misdemeanor contempt of court, a crime for which he was
pardoned by President
Donald Trump on August 25, 2017.
[15] In a separate racial-profiling case which concluded in 2013, Arpaio and his subordinates were found to have unfairly targeted
Hispanics in conducting traffic stops."
Not exactly a ringing endorsement of him. I also looked at various opinions of Trump pardoning him and most condemned the pardon and a few praised it.