Why, from first principles, should YouTube allow this? Why shouldn’t they go thermonuclear? I understand ads are annoying - I block as many as I can! - but I’ve never seen someone put together a coherent defense of the practice.
On Youtube, it's convenience and unwillingness to either pay or stop using the service. I don't have a problem being unethical to Google, but I will probably end up paying once my adblocker no longer works on Youtube.
Many people have literally grown up with Youtube, and a large section of them have used ad blockers for most of their lives. They see the adblockblock on Youtube as an attempt to take away a service that's supposed to be (ad) free, because to them, it always has been free. When you see Youtube as the free, unlimited repository of videos that the internet provides you with, forcing minute long ads on Youtube would feel like putting billboards in a national park.
The same is true for many other services. Everyone is mad that Netflix wants its customers to pay. The best stretch I've found is that Netflix tweeted "sharing is caring" once, but sharing accounts within a household has always been allowed.
In their attempts to undercut the competition by shedding money to provide services for free or for cheap, large corporations have cultivated a large audience that expects everything for free with no contribution from their end. Fifteen years of free, almost ad-less service, is a long time, and it changed the culture of the internet.