An accusation of virtue signalling is usually a point of order designed to force the signaller to desist from grandstanding about how virtuous he is; how terribly enlightened he is by the definition of the politically correct orthodoxy.
Virtue signalling like most ad-hominems is a desperate appeal to popularity in an attempt to hide from objective reason. That is why we see so much of it from politicians.
An accusation of virtue signalling is quite simply a challenge to make a point if you have one. Stop trying to win lazy points with the audience by hiding behind something that is irrelevant to the debate.