Age Discrimination
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.