TV is not as passive as it seems - there is evidence that it is a stressor on the brain which leads to fatigue (it's not as relaxing as thought - more like a drain of mental energy) because of the constant stimuli to new images. Consider getting rid of the tv, not just turning it off. He'll find other things to do with that time, probably even include you in it!
I trashed my tv twice in my lifetime, which happened to be two of the most productive and sane times in my life. Coincidence? I think not!