Because more money to spend by Mozilla means more and better products for its users. Minor inconvenience in UI will result in overall larger benefits for the userbase. It is obvious if you put aside the ads-hating generators.
what comes after "ADS", "BETTER ADS" then "TARGETED ADS" then...
so, they should say it to "their" [what's left of em'] users face, don't you think so?
did you ever expected THIS kind of DOGGY release from MOZILLA?
I have NOT expected that Mozilla will release their canines into the wild internetz. That definitely may contradict generally accepted paradigm that internet is feline-dominated.
And yes, I think that if you focus on the global context of the activities of Mozilla, ads will be a net positive for users.