I think the situation for Conan lies more on catching the criminal. Conan isn't the law, but he follows the law. This kind of situation is similar to the police system in real life. The cops are merely there to uphold the law, but they do not sentence you. The judicial system is there for that reason. I do think that his mentality on the issue could be a little less black and white. But I think that they do it to progress the show. Conan only seeks the truth. There have been instances where his logic had been blinded, but in the end to him a criminal is a criminal. I would definitely like to see them expand on Conan's views for sure. It's just way too solid, and dare I say unrealistic for a show such as this one.