It's wrong to kill people, if you do so, we will execute you. (Slashdot is quite US centric and the US still uses the death penalty.)
I'm against the death penalty myself, but the above is an oversimplification. The actual policy is more like "It's wrong to murder people, if you do so, we will put you to trial, and if you're found guilty by a jury of your peers, and all of your subsequent appeals are denied, then you may be executed".
The key distinction being the (alleged) operation of due process and rule of law leading up to an execution, as opposed to the ad-hoc extrajudicial killing in the case of an individual committing murder.
Unless you observe the distinction between what the law is allowed to do vs what an individual is allowed to do, the logic fails under its own weight. For example, you could use the same construction to accuse the US of hypocrisy for uncontroversial practices: "it's wrong to kidnap people and keep them in a cage; if you do so, we will imprison you", or "it's wrong to take money from people against their will; if you do so, we will make you pay a fine" ... but I don't think anyone is (seriously) arguing for getting rid of all prisons or fines.