Linder and the people he represents "dream of the kind of community they want to raise their children in." They are not wealthy, but probably working-class folk who see Clybourne Park as their own first step up the ladder of middle-class success.
It is very important not to demonize Mr. Linder. Hansbury has taken great pains to present him as shy, reasonable, and in all respects (save one) respectable. He doesn't want to hurt the Youngers, and believes truly that he is doing the right thing by offering them an option. As he phrases it, the dream of having a safe place to raise one's children is identical to the dream expressed by Mama. That is the point.
He does not say or imply that he will not be responsible if certain elements "get worked up." It is a misreading to suggest that he is making threats. His last line is not a warning, but a simple "I hope you folks know what you're doing."
Doubtless Hansbury wanted to avoid alienating white investors and audience, and so deliberately worked to make Linder a non-threatening character. But by giving him the language she does, and constructing Linder's arguments as she does, she shows that the Youngers and their white neighbors-to-be actually have exactly the same dream.