>There's no such thing as "public" money; it always comes from private pockets and ends up in (different) private pockets.

That is just a play on words. Of course individuals are "private"; it's in their capacity as taxpayers (rather than volitional payers) that they collectively constitute the public. "Public" and "private" are terms from economics with established meanings.

>I can't see what's pejorative about taxpayer money. That's whom it comes from.

I don't want to get into a big discussion on this, but this is a good example of the distinction between connotation and denotation (http://classweb.gmu.edu/bhawk/101/semiotics/decon.html).