The problem is - they don't give a fuck about the hypocrisy, so all that's left is the ableism, from both those who regularly harm disabled people ignorantly using diapers to make whatever statement, and those mocking them for wearing them (and no one is going to ask them each individually about their medical needs, so you can never actually know if it is legitimate use or not). The impact remains - adults wearing diapers are the punch line, deepening an already existing and harmful stigma, for no other reason than a cheap and ableist laugh.