Not sure what you are whining about.....sounds to me like you acted like a sore loser and deserved to be banned from that league.
You said it yourself: "I thought this league is a joke so I made a few silly trades for fun because the league lost all its integrity at that point". I bet the other players in the league....all of whom had paid money to be in the league and were all still competing for a cash prize.....didn't think the league had lost it's integrity. And I bet they didn't find your trades "silly", either.
You absolutely deserve to be kicked out of the league if you throw a tantrum on the message boards and then making a bunch of ridiculous trades to try and teach the league a lesson just because you disagree with the decision of an unbiased commissioner (Yahoo, in this case).
And I bet the other players were thrilled when you were booted from that league. Yahoo may have lost you as a customer, but it saved the other 11 managers in the league as future customers in the process.
I get it, you didn't like how Yahoo handled a situation......and Yahoo might or might not have handled it properly .....but it sounds to me like they made a judgement call re: a dispute........which is their job as the unbiased commissioner of these league.......and you agreed that Yahoo would be the arbiter of all disputes when you signed up.
I understand that you disagreed with that "judgement call", but that doesn't mean it was unreasonable. And it certainly doesn't mean the league had "lost it's integrity".
By the way, very few trades actually deserve to be reversed.......even most of the trades that you think are terrible deserve to be allowed.
p.s. For the record, I agree that it is a bit harsh to lock you out of all your leagues (unless your tantrum was more extreme and your trades "sillier" than you portrayed them to be).......but I also bet that Yahoo has experienced enough situations where people booted from one league then try to sabotage all their other leagues.....so I sorta understand that overreaction, even if it isn't entirely fair.