Back in the days when the Principles and Purposes were being discussed at General Assembly, there was a significant concern that any statement adopted would "become a creed" in an explicitly non-creedal religion. Antiochian's OP shows that these concerns were well-founded. But please be aware that they are meant to be a clarifying purpose for the Association and our common activities as an organization, not an individual statement of belief. Historically and theologically that would have made Unitarians jump out of their skins to protest.
After all, the fifth principle is "the right of conscience"...the humanist belief that truth can't be handed down from above, it's the individual's conscience that is the ultimate ground of faith. If your conscience says that sociopaths and psychopaths (as an example) do not have inherent worth and dignity, a UU would certainly discuss the point, but wouldn't cut you off from the community.
After all, General Assembly adopted these principles, they weren't handed down by Moses. At GA a few years ago, there was a significant effort to totally rewrite them (which was voted down...thankfully, the new proposal wasn't nearly as good IMHO). They only represent our current consensus on our overall mission, and can change.
But it's important for any institution to have a statement of purpose--you've got to stand for something, or you'll fall for anything.
Having said that...
I believe extending the worth of persons to EVERY person is an important value. That doesn't mean we can't support throwing murderers in jail, that we should let them "do their thing"...that would be denying the inherent worth and dignity of their victims. It does mean that we don't torture or degrade prisoners, we hold out the hope that even the most toxic person may eventually be healed. Historic Universalist theology, after all, while it holds that everyone is eventually saved by a loving God, still believed that there would be a purgatory for those who had egregiously sinned during their lives. So it's not like we have to like everyone or what they do.