Short response: no, it's not wrong.
Long response: No, it's not wrong. Expressing one's self is all well and good, but there is no sane reason to not do at least a little code-switching in social situations unless you're literally always around the same sort of people.
The moral of "Be Yourself" always struck me as sort of misplaced. In American and other individualistic cultures, it's always interpreted in a very broad way that really comes across as preaching to the choir (and in more collectivistic cultures, it's counterproductive). The real moral of "be yourself" is more along the lines of "don't be an obsequious boot-licker and/or succumb easily to peer pressure." Those sorts of acts are contemptible at best, self-destructive at worst.
But, just like in many cases, the overtones of a word or phrase don't usually keep up with its broadening meaning, so "social shapeshifting" seems to keep a connotation of "self denial" to, I would presume, most of the people who answered "yes" to this poll. It's really nothing of the sort.