Its against YouTube's TOS to download content, and to block advertisements. Another lesser known, and less enforced part of the TOS also covers content instructing how to download content and block ads. I'm pretty sure that's the reason YouTube took it down at least.
On another note, huge props to Linus for teaching how to block ads on channel and company, with a hundred mouths to feed, majorly funded by advertisments. I know he caught a lot of shit before with gamer nexus, but they deserve props for this.