The private sector includes people working at Wal-Mart and McDonalds, etc. who make $8.10 an hour...these workers don't have a government analogue.
If we're going to launch a complaint about salaries, at least make sure we're truly comparing apples to apples.
In addition to this bit of statistical chicanery, there are several others. Precisely because the government back-loads its compensation by paying bigger pensions later so that it can get away with paying smaller salaries now, civil servants tend to stay in those jobs longer than the private-market average, thus artificially skewing the comparison by falsely equating relatively senior employees among the former with relatively junior ones among the latter.
Really, there are enough legitimate grounds for complaint about government. Introducing specious ones such as this is to engage in boy-who-cried-wolf undercutting of one's own position.