Similarly, any person who doesn't put their retirement fund into junk bonds and penny stocks is also a con artist. After all, they are avoiding risky markets!
Arbitrage and market-making are legitimate businesses that provide liquidity to markets, making it easier for other traders to get fair trades. (Whenever you trade, the fair value is assumed to be somewhere between the bid and ask, so you're paying about half the spread on every share you trade.)
Of course, many hedge funds out there are scams that exist to take fees while taking ridiculous (and poorly-disclosed) risks with others' money, but not all of them are.
Do you really think that it's of benefit to society for some people to show up to work every day and take home Wal-Mart wages, instead of having real alternatives?
A large share of this government waste goes to military contractors employed in completely unnecessary wars such as the multi-trillion-dollar mess in Iraq.
Also, please cite your "on average double" statistic. If my memory serves me, the discrepancy is about 30% on average, mainly because private-sector pay is far more recession-sensitive. (The discrepancy would shrink, if not reverse, in a growing economy with a healthy private sector.) For the record, low-level government employees do make more while upper-level people make considerably less than they do in the private sector.
Given the prevalence of unemployment, yes Walmart jobs are better than at least one real alternative.