Fortunately there is no good eidence whatsoever that any of these "subliminal" methods ever actually work. If it did, then we would all have been brainwashed long ago into buying only one brand of car, milk, cola, and so on.
In fact, even the existence of a "subconscious mind" is far from established !
I do think that the way many parents use the TV as an electric babysitter, is bad for kids --- not merely because much Tv programming is shallow rubbish, but because so long as they are watching it they are not doing anything else more useful, like reading books.
On the other hand, I don't think kids ought to be excluded from TV --- use it wisely, let them see useful programs, and use others which may turn up as opportunites for discussion about unpleasant realities in the world.