What do people mean by "never forget"

Today I tweeted that I didn't understand why so many people want to "never forget" 9-11. It seemed to me that what I was reading on facebook and twitter was that people wanted to keep an eternal grudge match. Obviously, I misunderstood a lot of people, but I also think it's true of some other people. So what do people mean when they say, "never forget"? Do they mean never forget the people who died and suffered? If so I back that 100 percent. On the other hand if they mean forever hold a grudge against a group of people that we can never truly get back at then count me out. Especially if that means creating a racial divide with everyone of middle eastern decent.