From a new paper by Justin Tosi and Brandon Warmke in PPA:

Our basic contention is that one grandstands when one makes a contribution to public moral discourse that aims to convince others that one is “morally respectable.” By this we mean that grandstanding is a use of moral talk that attempts to get others to make certain desired judgments about oneself, namely, that one is worthy of respect or admiration because one has some particular moral quality—for example, an impressive commitment to justice, a highly tuned moral sensibility, or unparalleled powers of empathy. To grandstand is to turn one's contribution to public discourse into a vanity project.

I will resist naming the professional philosophers who should read this, but you know who you are (or at least your colleagues know who you are)!  The paper also incorporates a useful discussion of group polarization, which as we've noted before, is quite relevant to the phenomenon.