OK I agree with you, but let me play devil's advocate a little?
Varoufakis and others have said that it is very easy to say "just take the pain" when you are not the one who will have to live the next 5 or 6 winters without fuel to heat your house or cook food. Any solution must be the best one possible for the Greek people. There are thus more or less three options:
1. Staying in the union and refusing to implement austerity, perhaps till the EuroGroup kicks them out (in which case I propose the George Costanza solution: just keep showing up to the meetings after you've been fired)
2. Storming out of the union, in which case they would have to default, immediately nationalise the banks and implement draconian capital controls. In this case, it is entirely unclear what would happen legally to everything from private contracts in € to existing trade agreements. Millions of hours of work for lawyers.
3. Planning a managed exit with the Troika, trying to squeeze as much liquidity and time out of the ECB to keep basic services running, pensions paid, humanitarian aid (very much needed), etc. Even this plan would take a matter of years according to most analysts.
So which option would you prefer, or do you have a better idea?