It¹s a sad fact that bikers are lumped in with armed robbers at petrol stations and can¹t get served until they've taken their crash helmet off.
But what to do if it's a flip-front lid and you still get trouble? Go to the top.
A reasonably worded letter to the Chief Executive of the fuel company pointing out that the design of your helmet allows the staff to establish your identity on CCTV before they activate the pump, will at least allow you to make yourself heard.
Although I suspect their response may be that you can flip the front down in a second to make yourself anonymous and that it's company policy.
In which case, use your right as a consumer and take your business elsewhere in future if common sense won't prevail.