I fail to see how you can ban a sign like this - it would need the Thought Police to know beyond reasonable doubt that the gesture was meant as a hate message, or simply that someone was indicating 'OK' in an ages-old accepted manner.
I clue is pretty much who is doing the signing - if it's a mum signalling to her her child at the school gate as they go in, then it's probably OK, if it's a scowling hulk with a shaven head, dead eyes, and swastika tattoos on his face, then probably not.
Simple enough for those self-obsessed numpties with too much time on their hands looking for trouble to take on board?