So check it out.
Soul Calibur is having a few more big tournaments, however they've all
AS A COMMUNITY banned Hilde as she was giving SC4 players fits in the same way MK does to SSBB. (Not because she was an insurmountable problem, but because she was the equivalent of SSBBs MK in that you have to change how you play completely and train specifically for her).
This decision was made to keep the tourney going community happy, however this wasn't just a isolated regional thing, this was agreed upon by quite a few areas before making it a standard for all upcoming tournaments.
SSBB's community uses what ruleset? Allowing MK? Then I would say, as a third party, you should allow him.
Don't want to travel and/or don't CARE about people who travel? (either traveling in or out) Then make whatever ruleset you think is the best. (BOWSER ONLY, ONE ON ONE, NO ITEMS, FINAL DESTINATION)
Bear in mind if you do make your own banning MK rule you're shooting yourself in the foot as far as people who play SSBB outside of OK are concerned. You won't get people coming in for tournies (hypothetical: "They ban MK? hahahaha... guess who has two thumbs and isn't going to THAT tournament? THIS GUY~!!!!") , and you won't get people who are fully prepared to travel out to tournies.
Just think about what you want here in Tulsa.
Conform to the community standard and continue down the path you're currently on (losing people because they don't want to have to deal with MK but adhering to the community standard and staying on the 'national SSBB map' so to speak).
[ - ] Locals, [ + ] Travelers
Ban MK and possibly lose out on the whole 'being an active part of the community' thing (losing outside people due to not wanting to travel to a tourney due to wonky rules, but attract the 'ol locals back).
[ + ] Locals, [ - ] Travelers
...and to help you decide I have THE MOST METAL PICTURE EVER: