It's really pretty simple: Adblock hurts those that rely on advertising revenue to run their sites. Hurting a service, even if they are already making a lot of money, that you are using -- is, imo, wrong. The cost to run YouTube is in the millions.
(I use it selectively on, and only on, extremely intrusive ads.)
(I prefer a model that allows those that don't want to see ads at all to pay a website operator to have them removed. )
Guess I will uninstall adblock. I mean I knew what I was doing, but seeing it put so succinctly makes me think I shouldn't be doing it.