I'm really sorry to hear this. Heathrow has typically been a little more tolerable than some other AA stations in Europe.

I think that you should send something not just to AA but to the station manager for AA at Heathrow. Tell him or her that you are going to stop flying American because of this behavior. I think it's also appropriate to say that you have posted your experience on the internet and have advised frequent flyers to avoid American at London/Heathrow until changes are made.

The more elite passengers who complain, the better. There are certain layers of security required by the FAA for US airlines departing from "extraordinary risk" airports. BUT American has a say over how much of this screening is conducted and the attitude of its contract screeners.

I think that American recently switched to an all-ICTS contract for Europe (I'm not sure, but I recall reading a press release.) American can therefore tell ICTS that its passengers are unhappy. ICTS is not the only shop in town, so you and American have some leverage.

As I often say, the screeners can get away with being more intrusive if they are polite and friendly. Power trips do not enhance security and are an insult to the passenger.