Quote 1
LINDNER (Turning a little to her and then returning the main force to WALTER)
Well – it’s what you might call a sort of welcoming committee, I guess. I mean they, we – I’m the chairman of the committee – go around and see the new people who move into the neighborhood and sort of give them the lowdown on the way we do things out in Clybourne Park.
BENEATHA (With appreciation of the two meanings, which escape RUTH and WALTER)
Un-huh. (2.3.47-48)
Notice that Lindner says that he's here to tell the Youngers "the way we do things out in Clybourne Park." This hints at the fact that he thinks of himself and his white neighbors as separate from the Youngers. Beneatha picks up on this, detecting impending racism before Walter and Ruth do.
Quote 2
LINDNER
…most of the trouble exists because people just don’t sit down and talk to each other…That we don’t try hard enough in this world to understand the other fellow’s problem. The other guy’s point of view. (2.3.59)
Karl shows how hypocritical and racist his logic is. He sets up the actual proposal by suggesting that the Youngers consider the Park Association's point of view, not the other way around.
Quote 3
LINDNER
.... I want you to believe me when I tell you that race prejudice simply doesn’t enter into it. It is a matter of the people of Clybourne Park believing, rightly or wrongly, as I say, that for the happiness of all concerned that our N***o families are happier when they live in their own communities. (2.3.65)
Karl Lindner tries to convince the Youngers that segregation is in their best interest. He's not so sure they'll buy this argument. So, Lindner tries to make it seem like none of this was necessarily his idea, and that he's just the messenger there for the greater good of all involved. Unsurprisingly, the Youngers don't buy it.
Quote 4
LINDNER (Looking around at the hostile faces and reaching and assembling his hat and briefcase)
Well – I don’t understand why you people are reacting this way. What do you think you are going to gain by moving into a neighborhood where you just aren’t wanted and where some elements – well – people can get awful worked up when they feel that their whole way of life and everything they’ve ever worked for is threatened. (2.3.80)
Mr. Lindner and his neighbors see the Youngers' presence in the Clybourne Park neighborhood as a threat to their way of life. When he notes that certain "people can get awful worked up," he's calling attention to the fact that these sorts of situations can sometimes lead to violence. Is Lindner just recognizing a known fact? Or does Lindner mean this to be a subtle threat?
Quote 5
LINDNER (Almost sadly regarding WALTER)
You just can’t force people to change their hearts, son. (2.3.83)
Karl Lindner thinks it's impossible to change the minds of the white people – yet he's asking the Youngers to change their minds by abandoning their dreams. We think it's interesting that the playwright lets us know in the stage directions that he says this line "almost sadly." Could this mean that somewhere inside him he really can see past the walls of racism? Does he recognize how wrong what he's asking of them is?