What you are missing is that by calling you, personally, sexist, people aren’t advocating for political change. They’re asking you to not be a dick and not discriminate/generalize based on gender/sex, which is what these memes generally do while also mocking female-identifying persons as being boring and vapid while male-identifying people are quirky and fun.
(usually these memes tell on themselves by stemming from a place of not knowing enough women on a personal level, but I digress)
Arguably not free, seeing as they’re making a ton of money by selling our data.