AMP turned me down for an account as I am 74 years old. I have been trading stocks since I was 24 years old and traded futures the old way, with Ira Epstein in the 90's. This is age discrimination!! I am financially stable, and able to withstand any losses I might have. Risk is not a factor for me.
I'm not a lawyer and I'm definitely not your lawyer but... if they turned you down soley based upon your age then you probably have a good lawsuit. The way I see it, you can either find a lawyer of find another broker. The latter is probably a lot cheaper and easier.
IMO, sign up with two other brokerage firms and fill in the application exactly as you did the first; word for word. If the second two accept you, sue the first one that rejected you and make them prove that they did not in fact use age as a discriminatory factor. Then watch their insurance firm settle out of court with you in three years time - it will happen about three hours before the scheduled court date appearance. My 2 cents.