The defense bar and "civil rights" groups have been complaining for years about the government's use of "sting" operations. Typically such operations are used to catch drug pushers; the pusher thinks he's selling to your garden variety addict, who instead turns out to be a DEA or FBI undercover agent.
The characteristic objection to sting operations is that the govenrnment shouldn't be using stealth and deceit. Often the objections are bound up with more general complaints about the fact that drugs are illegal at all. One often hears as well the criticism that stings are entrapment.
In an ideal world, I too would have heartburn about the government's using deceit. But an ideal world doesn't contain the sorts of people I spent years dealing with in the US Attorney's Office.
In particular, it doesn't contain folks like this, who, very fortunately, was arrested today as a result of a sting. Perhaps those up in arms about operations like this will reconsider, although I concede that this is more likely to happen if they had been planning a trip to the Capitol Visitor Center.