Yes, there is a place for a discussion of ethics outside of the current legal framework, and if the Constitution is found to be lacking in that area, then it should be amended. Until that happens, our government is legally bound to abide by the Constitution as it is written, and to judge whether or not that is happening, the document must be interpreted. One important aspect to interpretation of a document is to understand the circumstances under which it was written. To do that with a 200+ year old document requires a little knowledge of history.
The framers of the Constitution did not achieve perfection, but at least the idea of the "rule of law" does give us a relatively consistent and stable society in which to live. The disadvantage is that written law is static and cannot quickly adjust to changing circumstances. Ideally, we would have an enlightened leader who knew the right thing to do in every circumstance, and would govern with perfect justice. If we could be assured of that kind of government, we wouldn't need to worry about interpreting documents.