MEN ONLY!! Can someone explain to me the comradrie over fidelity attitude among men...especially married men?

My husband has a new co-worker who was moved from another "department" and the reason for it was because he was fraternizing with the trainees which is strictly forbidden not to mention he's a married man. My husband explained that the reason he got caught was because a friend/co-worker "hacked" into his email and forwarded it to his superiors. He was subsequently demoted and moved. My husband seems to think that in matters involving infidelity that you should remain a friend and keep it to yourself because it is after all "their business". Or if morality is important to you then to pull that friend aside and urge him to stop. In my experience, a lot of men would see that too as some kind of betrayal and that person would just be one less to confide his dirt to. How can men accept this mentality of comradrie over fidelity? Is friendship that important that you should brush these things under the carpet? Furthermore, if this is the position that my husband takes on the matter, should I be worried about him and the company he keeps?