Sorry to hear that. I work at an ASP in Germany and we certainly do not treat our customers in such way. However, I do believe that there is no law that states that a company must sell you a product, therefore I would not call it discriminatory. I agree - it is very unprofessional and not customer-friendly - but imho they did not discriminate you. If I were you, I'd simply quit shopping there.
*EDIT*
And usually some companies have some sort of "Feedback" page on their website. Fill that out and tell them how unhappy you are and that you made your purchase elsewhere. At least in my (pretty big) company the management reads every feedback and then distributes it to the store in question so that the store managers can improve (or get shouted at for not selling an item

)