Readers sometimes write to ask how a certain ad got onto my blog. You know, I don't see any ads at all when I read my blog. Or anyone else's blog. Or, basically, anything on the Internet at all. Now, how could that be?
Am I stealing because I avoid ads in all aspects of my life? I don't think so. In fact, if a company forces me to watch an ad — this happens on airlines now, when you first board — I feel I should be paid for the experience. If you sell my work or my time in order to make money for yourself, my feeling is you're stealing from me unless you compensate me satisfactorily.
But no, blocking ads is not theft of service unless seeing those ads is made an explicit condition of accessing some service. And if it is, I will probably not use that service or visit that site, just as I don't watch commercial television any more (I stopped around 15 years ago).