I would report that in a second; particularly if he's doing it on duty. I've seen guys get demoted and/or fired for that. F'em. I don't want to work with people that brazen about it. If I need help, you better not take a second longer because you're pulling your pants up.
In my work I work closely for a long period of time with a lot of different professionals in every field.
I haven't found one that is more or less prone to cheating these days.
What I have found is that cheating is rising at an alarming rate over the past 14 years. Everywhere.
Some psychologists and sociologists have speculated that the rise in cheating correlates directly with the rise in tech toys because cell phones, computers, etc, make it much easier to cheat, for a longer while, at least until the person is caught.
IMO, a cell phone is a huge culprit because you can buy burner phones, and even a person's regular cell can be a password protected hotline.
Also, the people having affairs can text and email, even as they lay snuggled in bed with their spouse watching TV, as mine did.