All bollocks. Certainly at our aero club there is no mandate to stop sales. However, some aero clubs do enforce the policy of the person(s) wishing to purchase avgas must produce at motorsport licence of some kind. Most clubs do not enforce this however. I cetainlly do not ask

I have my own avgas fuel card. Easy to get. avgas is (I recall $1.78 litre plus GST). This will be cheaper than just turning up and buying from an aero club.