Broadcast (over-the-air) television in the US must conform to FCC rules (we have something similar here in Canada). Under penalty of fines, content must not exceed certain boundaries. Movies produced for theatrical presentation must be rated; children may not be unaccompanied (if admitted at all) to movies of certain ratings. When a movie (such as Deadpool) originally produced for theaters comes to TV, it must be cleaned up for regular commercial broadcast.
Cable is a different matter. Cable isn't treated like over-the-air broadcast, so is not subject to the same content restrictions. That is why cable-only channels (like FX) will often carry more permissive content. If you're on cable, you might watch a movie on a channel that is basically an over-the-air channel distributed on your cable service, and find the movie heavily censored, but find the same movie presented uncensored on a cable-only channel.