Tweeting a picture isn't a DEFCON 4 response. I don't really think that it's that problematic- they were breaking the rules of the conference that they had agreed to, and calling someone out publicly is a very common method of enforcing social norms. It's not necessarily the most nuanced or feel-good method, but it's not like they had an expectation of privacy while in a crowded convention room. The overreaction here came from the guy's company, and we really don't know the whole story there.