Age discrimination happens all the time and people can stomp their feet and shake their fists, but it won't change the fact that it does happen.
If you sense a company won't consider you because of your age, why would you want to work for them in the first place? By demonstrating they don't value your experience, they've done you a favor.
Thank your lucky stars you got to see it early on then just wash that dust off your shoes and keep moving forward.