Your logic is flawed. The real reason you can't play the game is because Ubisoft choses to prioritize their needs over their customer's. Here's the logic:

• a SMALL number of people pirate this and other games (PIRATES)
• a LARGE number of people purchase the game to play it (CUSTOMERS)
• a COMPANY seeks to stop the SMALL number of people from pirating (UBISOFT)
• the COMPANY forces the LARGE number of people to use DRM
• a TINY number of people DDoS the COMPANY'S DRM server (HACKERS)

Of this group of entities, PIRATES, CUSTOMERS, UBISOFT, and HACKERS, only the CUSTOMERS are being hurt at the moment by the DDoS. Indirectly, Ubisoft is being harmed because people like me who purchased their games in the past, will not do so in the future. They may or may not see this as harmful to business.

The pirates, while definitely at direct fault, are only leveraging the ability to affect the masses to further their end goals. They are, in fact, not whining at all. It's the customers who are affected by the hacker's action who are whining, as they well should.