Principles are fine shortcuts to avoid having to stop and analyze every situation, but some people use them as crutches to avoid having to weigh competing values.
Instead of using the Constitution as a reason to oppose some government action, why don't you try the mental exercise of justifying your position on the practical impact that the action would have on people's lives. If the Constitution is as unerringly sacred as you believe, it should be easy for you to show that the Constitutional position produces the best results for real people. When you are able to do that, you won't need to use the Constitution as a crutch.
I see.... so principles shouldn't really be principles at all. They should just be some kind of loose guidelines, to be abandoned for whatever pragmatic "competing values" come down the pike.
No wonder the country's abandoning the notions of rights and constitutional restraint.
Two things. First, the Constitution is the law of the land, and every member of Congress and the president swear oaths to uphold it, so any politician who doesn't follow it is by definition a liar and not to be trusted.
Second, you can't trust any and all future politicians to do what'd right, which is why they must be forced to obey a set of limits. It isn't so much that they can't be trusted to know what right (although they can't be trusted for that, either), they can't be trusted to do what's right. If I were a politician, I would not exclude myself from that. All of them must be limited.