The bank wrote that contract, after all, and the bank was definitely the party with more power, so they're getting exactly what they insisted on. Go ahead and give it to them:
While there are certainly financial and credit consequences to walking away, it pisses me off that people are taking the position that this is in any sense a moral issue. It's simply a business contract, and when you break a contract, you suffer the specified consequences.
ETA: As I mention above, there are consequences to walking away. And you'd better know them before you decide. So yes, talk to a specialist real estate lawyer to make sure you know precisely what they are. Don't assume you know the rules; in some cases, the bank may be able to go after your other assets, not just the house. But while losing everything you own might be one of the consequences, being a bad person isn't.