Good advice, albeit hard to accomplish. Identity is a core part of political party formation, at least in Europe (together with self-interest and ideology). No doubt it has an important role in marketing as well. I don't see these forces giving up on pulling the identity lever any time soon, it seems to gain importance if anything.

However, perceived identity coupled with a sense of oppression, exceptionalism and/or fear of extinction is what always gets us in trouble (i.e. war), so there are a number of good reasons to keep tight reins on identity.