What is one man / woman's " principles ". is often another's sin / vice / corruption, or worse. The Taliban had their set of vaunted " principles ". They certainly aren't the same as an Orthodox Jew's ! Dem's " claim " to have " principles "; they certainly are NOT the same, by and large, as those of Conservatives.
Not even the Founding Fathers stuck by the so called " principles ", that so many here claim they had.
There is but one principle to live by, and it's not as subjective as you think. It is to conform your life to God's will. Being "principled" means not accepting an argument that conflicts with what you know to be right. It's not sinlessness; it's recognizing that truth is not relative, and making it your business to stand up for it.
And yes, of course we all fall short of this in our lifetimes, but to be a principled person you still strive to do the best you can.
Just because Bush did not veto CFR and on reflection decided to involve the 3rd leg of the constitutional government to exercise its constitutional duty does not make him "unprincipled" it just meant that he decided on a different course of action than you may have.
It is unprincipled to take an oath of office to uphold the constitution, and then to sign a bill that you say violates the constitution. If the constitution doesn't matter, let's just say so.
Incidentally, what you're arguing is bordering close to Neitzche's existentialism--that is, that there is no right and wrong, only circumstances to which we adapt in whatever way that pleases us. I hope you don’t really believe that, 'cause if you do, I take you up on it on another thread.