Its not cool to make someone feel bad about stimming. We all do funny little things when no-one is looking; hello, ever picked your nose in the car, scratched your groin in an empty store isle, deliberately stepped on something on the ground just to hear it crunch... The trick is to see if you can quietly teach substitutions in behaviour. As soon as you attach shame, the stim is reinforced, and even harder to extinguish or swap out.
I really dislike the grunting stim, a series of quiet gutteral throat clearings, it gets on my nerves! I have been trying to teach that practicing this limits the breath. When a real anxiety situation presents, the anxiety is already primed to jump in. Breath is an integral part of meditation & stress reduction practices. Try it right now: take a deep breath in, all the way to the bottom of your lungs. Notice you instinctively sit up straighter to do it. Let the breath go out slowly, 3-4 times slower than it came in. Do it several times, feel the oxygen pour in, makes you feel brighter, makes your heart rate slow slightly, makes you feel a bit light-headed even. That's the kind of energy needed to make decisions.
We've all been in crisis at some time or another. Your heart feels like its going to leap out of your throat, beating so hard & fast its revved right out, talking mile-a-minute or so breathless you can't talk. I feel anxious just re-reading that. Thats a mind-body connection. It can be learned to tune into it, to acknowledge it, to let it wash over without reacting to it. My son has to learn this over & over & over again. It doesn't stay with him, there's a gap in his memory I can't figure out. He's really resistant to letting go of the grunting, because it makes him feel good, and because he's not aware he's doing it sometimes, and because he likes it. Its human nature to learn & relearn what we like, there's comfort in that. No one likes to be told what to do, what to learn, what to say. The challenge is figuring out the block, to understand it, before knowing what comes next. Sometimes it makes sense right away, often it needs to be set aside to percolate on the periphery while I do something else.