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.
With a weak identity you can just hop over to the winning side. I think a lot of polemic attacks over identity aren't aimed so much at the opposition, but at weak supporters to stop them defecting.
there is a prisoner's dilemma type of effect here where, when other people are "defecting" (wasting fossil fuels and packaging), it's rational for the individual to defect as well.
I don't get that, though: there's little to no penalty in this case to avoid "defecting". Things may cost a little more for you, but it's not nearly as drastic or dire as the expected outcome in the actual prisoner's dilemma if you don't defect.
consider that the cost of complying is immediate and borne by the agent, whereas the penalty of defection is discounted according to the degree to which people believe it can be postponed (insofar as they consider the penalty at all).
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.