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.