Q,
I would disagree with you partially.
There are instances where immigrants have won cases when the govt agencies didn't follow the law and the govt can argue and make their case but certainly if they act in a rather meaningless and nonsensical way and the case can be made we ( immigrants) can win.
Unfortunately there are few instances where practically it has happened.
GC can be revoked only when there is fraud. while its easy to delay a case and investigate before approval, after its approved there needs to be clear evidence of fraud or other reason to revoke something. especially after GC or citizenship are approved.
while your knowledge perhaps might be lot more than I do, I like to see nay actual cases of GC/ citizenship revoked without a good reason