I use ads on my OSS projects' websites so to the degree ad blockers block low key, non intrusive ad networks favored by OSS projects like Ethical Ads and Carbon Ads, they are hurting regular people
The ads that pop up when I scroll, or ads between every paragraph (or more) or ads that are animated or use fancy CSS to overlay the main content or slide in from the side and float around -- those are what make me run an adblocker.