Moving the goalposts

One of Steve Sailer’s readers makes a perceptive observation concerning the media’s behavior in the Trayvon affair:

Has anyone outside the Steve-o-Sphere noticed that, in typical fashion, the grounds for outrage keep subtly shifting?

Month 1- “A crazed white vigilante murdered an innocent, angelic boy!”.
Then it turned out that Martin wasn’t so innocent or angelic, and was
for all practical purposes a man, not a boy. Zimmerman was also revealed
to be not so crazed and not so white. So that angle was dropped.

Later- “It’s those awful ‘Stand your Ground’ laws, that’s what’s
wrong!”. But the defense didn’t even need to mention that law at trial,
because was totally irrelevant to the case….

This kind of “outrage distillation” is common when the press push a
bull***t narrative and then discover that they were mostly wrong. The
can’t continue lying, but they can focus the same amount of anger and
opprobrium onto smaller and smaller sins.

The anger remains the same, it’s the justification for it that remains a moving target. That process does sound rather familiar, for some reason.  I can’t quite seem to place it, though.