I absolutely agree that everyone who goes should enjoy the day, Christ knows every city fan here deserves a good day out after the crap we've had to put up with.
However the rest of your post makes little sense to me unless you're trying to justify something to yourself that you're not entirely comfortable with.
My choice, which I know puts me in a very small minority, is never to directly put money in the pockets of those who own MK Dons by going to a game there. (Using your analogy, if you're continuing to make a profit from something that's wrong, then I guess I can't see how you can have 'served your time'.)
I know that my individual action will have no impact on MK Dons, and I'm not here to virtue-signal or try to convince anyone else to do the same.
Regardless, I don't see how my belief hurts anyone other than me, because I'm sure it'll be a cracking day out. And I seriously doubt that MK Dons supporters will be crying to their dads because I'm not there!
Let's be honest here, you're never going to convince me that I should go, and I wouldn't dream of trying to tell anyone that they shouldn't.
What you're doing is exactly what you're accusing others of though, which is to try to make yourself feel better about it.
There's genuinely no need mate. Go. Enjoy. Win! Tell me about it later in the pub!