With your son, you get mad, suck it up or confront him, end up with hurt feelings all the way around, and a relationship that may or may not be repairable. 

If they are confronted with a reality that differs from theirs, they may react in a way to allow them to maintain their comfort zone and defend their reality, often by utilizing ridicule, insults, or derision to avoid further discussion and any facts emerging that threaten their position, beliefs, perception, comfort zone and feeling of authority.

When confronted, the tenant said that they are fake and only to create the illusion of someone's always watching To deter any wrong doing.

Every investor dealing with hard money confronts this issue directly.

I am a hands on, small time landlord doing about everything myself (but contracting out some skilled work)I find housing people worthwhile (and even profitable), but nobody would want a television show about it (think of a camera zooming in on me cleaning carpets or painting walls for hours....snooze)...In fact, I think if you do things right, you can prevent much of the drama (no building disasters or angry tenant confrontations) the staple material that would keep viewers riveted.My strengths would be in the day-to-day, nitty gritty details of small time landlording, especially for part-time landlord that holds down a day job.

Getting confrontational won't help his, or your situation. 

You've been so direct that they started to confrontational with you?   

Or confront him with a warning but let it slide?

One that is not aggressively confrontational, but not afraid of confrontational.You need to be a professional.  

It could be cheaper than an eviction and be less confrontational, helping insure that you get the property back in the best condition possible.