Right, that's my point; from my amateur perspective, if it was illegal to grab YT videos without displaying ads, then it would be equally illegal to, say, show a blog post while not displaying the ads it tried to include. And since ad blockers are, AIUI, completely legal, it would seem to follow that it's also legal to download YT videos and play them without playing ads. (Of course, IANAL so maybe there's some angle I'm missing)