In a competitive market government should treat everyone equally by the same rules. Big banks do not exist in a competitive market as they are heavily shielded from competition, protected from failure, and massively subsidized by the government. As such they should be required to adhere to far more stringent rules.
I do agree that those rules should be transparent and not "unwritten" though.
Your comment is simply saying: contrast people who participated in the real estate bubble with responsible people who did not. I agree that the second group suffered because of the first and that this is unjust. Whether we can expect people generally to not participate in market manias to avoid such a predicament, is another question.
The problem wasn't so much that people took/were given loans they couldn't afford. Default rates fell for many years along with lending standards (not requiring a job, assets, or income for a loan became common). Continuous rapidly rising home prices kept defaults low. Believing home prices would always rise (at some minimum rate) made it rational for borrowers and lenders engage in this behavior.
To argue they were being irrational, you'd have to show that it was irrational for them to believe in the myth that this trend would never end, which is tantamount to expecting markets to not experience manias or bubbles.
It would be great to see the long term results as compared to buying less risky assets, like treasuries. It's not a question of whether the market's returns are positive over the long run, but whether they are positive enough to justify the additional risk.
I do agree that those rules should be transparent and not "unwritten" though.