No, Oktoberfest is not beneath the dignity of a former president because it represents a part of German culture. A president should celebrate all cultures, and this will be a perfect way to do so. Obama should take his family and have fun now that he no longer is president.
President Obama is a classy enough guy that he could pull of just about anything without losing dignity. I could picture him at Oktoberfest, indulging in a few beers, having laughs with the others there. Obama is a class act, and has a great way of showing that he's just a normal person like everyone else.
Some people don't agree with every decision that Obama has made, but Obama loves a good time. Obama has made it clear that he enjoys history and culture. For that reason, he should be allowed to go enjoy and experience culture around the world. Germany would probably be happy to host him.
Who won earth would actually think, Or even complain, that a former president visiting an Oktoberfest would be a bad thing? This seems more like a silly narrative to generate 15 minutes of fame then actually address a serious issue. There is no difference between hey regular person going to such an event and a former president doing the same.