The author is describing a reaction that began when he was still in college and Nixon had just become president. In other words, he had nothing to base this judement on. Sounds a lot like prejudice to me.
I would think that Nixon's history before he became president (congressman, senator, Vice-president, and losing Republican presidential candidate, the Checkers speech, the "kitchen debate" with Khrushchev, the JFK debates, his decades long anti-communism crusade, his HUAC investigation that eventually convicted Alger Hiss, etc.) might have let some form an opinion of him.
He wasn't exactly a "community organizer" stepping into the job after a cup of coffee in congress.