I can see what you're saying mate, but that's how the legal system is designed. The prosecution has to prove its case beyond reasonable doubt - it's not for the defender to make that judgement and it is his (or her) ethical duty to provide the best defence available to his client regardless of his own opinion. I sense that a lot of defence solicitors dislike their clients!
Regardless, the point is to make sure that the law is fair, proportionate, and that no one is denied justice on the whim of an opinion. A no comment interview is a perfectly legitimate response - these days I believe it's brought to the court's attention, and it's down to the court to decide on its significance when compared to the other evidence.
Remember that we're not far from the days when suspects were beaten for their confessions. If the wrong person is convicted (think Birmingham Six) then it's a terrible outcome for both the innocent and the victims, as all are denied justice. I'm sure you'd make a pretty decent solicitor Otis, but I'd perhaps avoid criminal law for now.