It was the assumption of the Democratic Congress in the 1970's that banks discriminated against particular groups- African Americans and Hispanics- based on race and ethnicity by denying mortgages to these groups.
The Congress also operated under the assumption that home ownership provides the best investment for individual American families.
Based on these two assumptions Congress passed the Community Reinvestment Act of 1977.
Another assumption held by most Americans in 1977 and in 2011 is that banks and bankers are greedy institutions that are blindly driven by an unceasing pursuit of profit.
I will return to that thought later.

As you read the part of the statute pasted below it is easier to understand if you substitute "mortgages" for the term "credit."

(a) The Congress finds that -
(1) regulated financial institutions are required by law to
demonstrate that their deposit facilities serve the convenience
and needs of the communities in which they are chartered to do
business;
(2) the convenience and needs of communities include the need
for credit (mortgage) services as well as deposit services; and
(3) regulated financial institutions have continuing and
affirmative obligation to help meet the credit (mortgage) needs of the local
communities in which they are chartered.

(b) It is the purpose of this chapter to require each appropriate
Federal financial supervisory agency to use its authority when
examining financial institutions, to encourage such institutions to
help meet the credit (mortgage) needs of the local communities in which they
are chartered consistent with the safe and sound operation of such
institutions.

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