Is it fair to use ad blocking software?

It is fair, but just as countermeasure for unfair ads. Because a lot of sites make certain abuse of advertisment, be it a billion banners, something opening new pages automatically or just very presistent ones. For example, I never block youtube ads, up to the point I see same 20-30 sec unskippable ad on EVERY video in my feed. To sum up: Either you use your ads responsively, or I use my tools responsively.