Again, HTC WARRANTS THE PHONE, Sprint provides the service. If you wanted Sprint to handle your warranty, you should have bought it from them. (Or paid Sprint for their insurance policy.) Just as if you want BB to handle your warranty, you wouldn't buy something from Wal-Mart.
Google gave you the phone. HTC built the phone. Where does Sprint enter into that picture? You may have a gripe with Google if they gave you a broken phone. You may have a gripe with HTC if they manufactured a defective phone. I don't see where you have a gripe with a company that was completely uninvolved in the transaction.
You signed a contract with Sprint for service, which they're providing, I assume, under the terms of the contract. And they offered you the option of insurance, which it appears you declined.
Does Best Buy ruin its reputation by refusing to fix something you bought somewhere else? I don't think so. People just don't understand the relationship between manufacturers, retailers and service providers.