Why should judges tear up contracts?

Shouldn't they enforce them:

House Judiciary Chairman John Conyers's bill, which is moving swiftly through Congress (and companion legislation introduced by Sen. Richard Durbin) would allow bankruptcy judges to modify home mortgages by reducing both the interest rate and principal amount on the loan. This would be a profound mistake.
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If Congress wants to deal with the rising number of foreclosures, it should not create a new mess by converting the mortgage crisis into a bankruptcy crisis. Doing so will open the door to a host of unintended consequences that will further freeze credit markets, raise interest rates for new home buyers, and spread the mortgage contagion to other types of consumer credit. Congress needs to reject this plan and look for better solutions.