It’s not the stabilizing brace they are after, but the short barrel. This is one step in the process of outlawing guns from the top down.
It is illegal to own a short barrel AR without a permit that costs hundreds (which is not a guarantee one will be issued).
The AR pistol can be used like a short barrel by putting the forearm brace against the shoulder.
The gubmint is always scanning the horizon to pick something to outlaw in the way of the 2nd Amendment. I believe the Founders said that which the government owns for protection, the citizens can also have, i.e., muskets, cannons. Of course, they didn’t envision B2s and M1 Abrams!
Thanks!