My question is why do the Catholics allow it? The majority of filth and garbage on TV is viewed by Catholics.
They're nominal "catholics". They might have been baptized into the Church as an infant, or adults might go through an RCIA program that, alas, is very anemic of the true Catholic Faith, but they're more interested in what the world offers them, not the true love of Christ which, as Bishop Williamson says, "is demanding".
Bishop Williamson:
The love of God is demanding, which is why people don’t want the real love of God. They want the nice, slushy chocolate human substitute. Let’s all just swim in chocolate until we fall into Hell.