one-womanizer

A man who constantly pursues a flirts with one (and only one) woman. Like a monogamous Don Juan.

Did you see that guy staring at his wife and ignoring the cheerleaders? What a one-womanizer!

Sowellsbane

A conclusion or idea so obviously bad that it could only be arrived at via broken formal academic study.

"Smoking cigarettes to expand lung capacity, once widely practiced, is now considered a sowellsbane."