MtGox is an exchange, not a bank. I'm mentioning this because there is an important third person with a bank: the customer, not the investor.
With mtgox, every customer is an investor. When bailing out a bank, however, the rationale is often to help out the people who cannot be blamed: the customers.
I'm still not claiming that bailing out I banks is a good thing, but the comparison you make is a small apples/oranges thing.
This sounds a lot like the too big to fail argument and so it is not an apples/oranges thing. It's a sliding scale and the only reason it seems like it is apples and oranges to you is precisely because MtGox isn't big enough.
I'm not saying that customers of a bank should suffer for the investment side but let the investors suffer for their bad investments, if the political will is there.
With mtgox, every customer is an investor. When bailing out a bank, however, the rationale is often to help out the people who cannot be blamed: the customers.
I'm still not claiming that bailing out I banks is a good thing, but the comparison you make is a small apples/oranges thing.