The answer lies in 1 Corinthians and Philippians 4:
All things are lawful for me, but all things are not beneficial. All things are lawful for me, but I will not be brought under the power of any. -- 1 Corinthians 6
Whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good report; if there be any virtue, and if there be any praise, think on these things. -- Philippians 4
Paul at some point told the Corinthians something that sounded like "Everything is permissible." He didn't mean that literally, but he probably said the same thing to the Corinthians as to the Romans about not being under a "written code" and the Corinthians interpreted that as "no rules!" (called "antinomialism").
But because a written code can never cover every possible situation--people invent new ways to sin every day--Paul gives us information on how to renew our minds to conform to the mind of Christ rather than to the world. When we put on the mind of Christ, we can look at each situation and determine the will of God...not by a written code.
Scripture does not say "watching television is a sin." But it does say, "not everything is safe for us to do.
It also gives us a prescription for testing anything that we might take into our minds and spirits.
Is it good? Is it true? Is it noble? Is it pure? Is it lovely?
Back in the early 80s, I watched what would be my last horror move, John Carpenter's "The Thing." After that movie, I realized that I had not done my spirit any favor at all. That put me behind in my spiritual growth. I was like a man running a marathon who stopped midway to smoke a cigarette. It took months for me to work that movie out of my spirit, and I realized I never needed to consume that kind of "entertainment" ever again.
An olympic athlete in training consumes only the food that will enable him to win. Sure, maybe a Big Mac won't hurt...much. But it won't help him win.
We who are in this race--we are in middle of actually running the race--must keep our eyes on the prize. We are not like a boxer who has no training plan and just beats at the air aimlessly. We must have a training plan and stick to it. We must feed our spirits the way an Olympic athlete feeds his body. We must constantly cast away all encumbrances that would hinder our running.
"Everything is permissible, but not everything is beneficial." We must always strive for the beneficial, not just the permissible.