Stimming is not a meaningless behavior. Talking to autistic people, over and over they've told me that being able to stim helps them focus and navigate their environment, and feel better overall. If a person is stimming, it's to serve an internal need - a need for sensory stimulation, a need for emotional self regulation, a need to express anything from frustration to joy. And by fulfilling that need, stimming helps autistic people to navigate our neurotypical constructed world.
Because stimming is not generally physically harmful (the pro-stimming argument is only intended to apply to non-harmful stims), many autistic people see inhibiting stimming as an effort to force a person to hide their autism and, therefore, hide and be ashamed of what many consider to be an inherent part of themselves.
I have heard many reasons as to why stimming should be eliminated or controlled (again, back to the "quiet hands"). But in the end, that's all they are. Excuses. Justifications for forcing a person to stop stimming towards the goal of making them seem "normal" even if it's by repressing something that they, adults and children alike, so clearly say they need.
Caley stims. Flapping, vocalizing, picking at a blanket, she's done it all for as long as I can remember. If a stim was hurtful, we worked to find another outlet, but other than that if Caley's stimming, I don't try to stop her or even redirect her. She's using a behavior to serve a function to help her and that's more than okay, that's great! I might offer a great big bear hug (the best I can do in that regard, at least, unfortunately my "little" sister is now bigger than me) to provide sensory stimulation and help support her if she wants it, but I wouldn't dream of telling her "quiet hands." Luckily Caley and I grew up in a household where the idea of quiet hands didn't even exist, but not every autistic person is in that situation, to their detriment. Below is an article from an autistic woman describing her experiences with "Quiet Hands" and how negative it was for her.
Hopefully after reading this post you understand. Autistic people stim, and that's not just okay, that's a good thing because stimming is a behavior that can help autistic people self-regulate and just plain feel good. Efforts to try to eliminate stimming are misplaced and, in fact, many autistics say that such attempts are hurtful.
Instead, I propose that we use our energy to eliminate the stigma of autism and therefore the stigma associated with stimming. Because unlike stimming, stigma actively harms autistics, whether at home, in the workplace, or at school. Share this picture to teach others the important function that stimming serves to help autistic people and comment with your loved one's favorite stim. Together we can make the world a better place for autistics and in this case that means a world where they can stim to their heart's content without worrying about how "loud" their hands are.