A bit Lufthansa bashing

A while ago I had bought an air ticket from Vienna to Madrid. There was a stop over in Munich because the airline - Lufthansa -  does not offer direct flights from Vienna to Madrid but I did not mind. My travel itinerary changed on the day and it happened that I was already in Munich instead of Vienna airport. So I thought Lufthansa must be happy to board me in Munich instead of Vienna saving fuel for the first leg. But no! The Prussian-like Lufthansa employee told me that I am not allowed to do this and boarding in Munich is impossible even though I have a ticket. I could of course buy a new ticket for 800 euro that would take me from Munich to Madrid! Byebye Lufthansa! Never again! What kind of passenger unfriendly policy is this?