I am not a lawyer, and I wouldn't usually defend them, but... [sticks head above parapet]
Humour me an analogy: Nobody likes it when a bailiff comes to your door. But the reality is that if there were no bailiffs to repossess property bought on credit when you didn't pay up, then no-one would loan money. For example, in countries where there is a cultural/religious aversion to repossession of homes, it's almost impossible to get a mortgage, and overall rate of home ownership is lower -- the law of unintended consequences here is that if you as a society refuse to kick people out of their homes, fewer people will actually be able to own their own homes.
I think a patent troll company like this is similar. Nortel engineers worked hard to invent stuff. Shareholders of Nortel invested in the company to pay for that stuff to be invented. The value of these patents as assets which could be sold off is in effect a form of 'embodied energy' created in Nortel. Remove the ability for companies like Rockstar to exist and to seek out license fees from stuff Nortel investors paid Nortel engineers to invent them in the past, and you've retroactively denied those investors from some of the return on their historical investment. The end result moving forward is that people will invest less.
Patents serve a purpose, as does their expiry. I could back a plan to shorten patent lifetimes for some classes of patents, but I believe doing away with the whole system would be counter-productive to innovation.