My personal belief is that it's fine to wear a hairstyle that comes from a culture to which you don't belong, as long as you take the time to at least educate yourself with a rudimentary awareness of where it came from, first. That's what I think a majority of people who lambaste cultural appropriation are getting at -- failure to give proper credit, or tendency to take undue credit.

If someone objects to a stranger's hairstyle because they have appointed themselves the de facto gatekeeper of that culture -- and they just want to find an excuse to be controlling of other people's actions -- then that's a problem. A problem bordering on racism, depending on how far a critic is willing to take their accusations.

I honestly prefer the "salad bowl" analogy over "melting pot."