"Managed bankruptcy" just means the company gets reorganized, slimmed down, whatever, by an outside party. The issue is that a company needs financing (huge loans) to operate during a bankruptcy: otherwise, they would miss payments to workers and suppliers, and they would never be able to emerge from that hole. Romney said they should have gone into a regular, private bankruptcy overseen by a judge, without the need for legislation, but that was impossible, because there was a banking crisis going on at the time (you might have heard about it). The only possible lender was the government. Romney opposed the only actually practicable way for the bankruptcy to proceed.