I believe you can ask the hotel to disable such channels when you check in. It's a good idea, if you're going to be leaving young people in their rooms while you do something else.
They'll just set a flag on the room, and the channels won't be available.
I am sure you can disable porn channels in your hotel room. You can't just access it without paying first. It is like Pay-Per-View, you have to pay to access see them. It is great especially if you have kids around.