Ad blocking is not theft. If it were, leaving the room with the television on while ads were playing would also be theft. Youtube is freely sending people content. No one is forcing Youtube to send them cat videos. No one is acquiring Youtube videos illegally via torrents.

Ad blocking is only possible on Youtube because Youtube insists on doing big data auction based advertising. If they wanted to, Youtube could embed ads in the video stream making it impossible to block them.

Youtube does not have a right to display whatever content they want on my devices. If they freely send me data, I have the right to display that data however I can on my device.

If Youtube wanted they could end the utility of adblock today. They could only send data to people who paid. They could embed ads into the video stream. It is their choice to make adblocking possible on Youtube.