Your assertion is that the US should not arrest someone on US soil for crimes committed against US citizens by the person while they were in another country. That doesn't make sense to me. If an American was mailing handguns that are legal in the US to people in the UK I think no one would have a problem with them being arrested if they visited the UK. Disagreeing with the laws of another country is reasonable and your home country has the ability to at least try to intervene in your behalf. But when you are traveling to another country you are subject to its judicial system. If this minimum of enforcement is not acceptable how are any of us to defend ourselves against criminals in developing countries that will never enforce their own laws?

The concept that we get to take our home legal system waltzing around the world with us as we travel is arrogant. You may be morally and legally free to post a cartoon mocking Mohammed on your Facebook page, but don't be surprised if you get detained on a trip through Saudi Arabia.

At least in the US he's innocent until proven guilty and will probably get a fair trial. And he wasn't arrested for posting his opinions on social media or bashing the president. The software in question was designed to steal people's access to their shopping and banking accounts. And the accusation is he conspired to sell it and offer support to criminals to help them abuse their victims. I would have no problem with an American getting arrested under similar circumstances while visiting another country.