Well, people only have their experiences to judge by, and really that's all that's relevant anyhow. Can you at least acknowledge that a black man growing up in the deep south in the 60s, might have every right to lament a rather horrific upbringing, and that there is no reason or excuse to minimize the horrors he felt from the deep racism he experienced, just because you had a different experience, or somewhere in South Africa someone had an even worse experience?
How about urban youth in high crime neighborhoods that really do live in fear of the police? Gonna tell them they're overeacting? Have you honestly ever had to deal with constant harassment, trigger happy police officers and living with the real fear that one false move, one suspicious bulge in youe pocket, one wallet that is misidentified as a gun, can result in your death? What if you had to deal with stop and frisk policies (being automatically searched regardless of suspicion of a crime), wouldn't that infuriate you, and probably have resulted in a far greater chance you'd get arrested for something petty like having a dime bag in your pocket, something that the kids on the nice side of town get away with all the time?
Sometimes you have to live it or see it to understand and believe it. Recently there has been all this scandal about police brutality, which minorities have been complaining about for years. But it wasn't until phone cameras came along and showed it to people, that large parts of the population where finally like, "omg that's horrible, I thought people were just exaggerating." Meanwhile, large numbers of black people are like, "what the hell did you think we were complaining about all these years??? Did you think that we were all just making it up?????"
Are you gonna tell the Latino immgrants, who now are subject to ICS roadblocks only in their part of town, who have to carry around immigration papers to avoid being locked up whilr ICS agents sort things out, that"hey its not so bad, you know the Palestinians have it even worse."
I sincerely don't understand why you think, for any of those examples above, asking people to acknowledge Americas greatness is necessary, or even relevant to these peoples experiences. It's nothing but patronizing and dismissive. Period.