But when you hear people talk about human dignity, it's usually colored not by the consideration of the Divine image in man and his supernatural vocation so much as by the liberty due to him in his natural powers.
So what's the effect of that coloring of the term? Well, it makes the term serve a certain conception of justice and human rights, according to which the basic thing to be sought is self-determination. Since human dignity stems from the Divine image, which is in the possession of intellect and will, and intellect and will are naturally free, the safeguarding of human dignity somehow becomes about guaranteeing the liberty of the intellect and will, and therefore about maintaining a sphere of individual independence over and against any community or law that could subordinate the individual convictions and desires of a person to some higher good.
This is why people get so freaked out by Dignitatis Humanae. Because if you read it superficially it seems to go down exactly this path.
And the problem with this path of thinking is that, while it's right in its principles, it fails to consider that the human faculties of intellect and will, while free by nature, possess dignity not on account of their liberty but on account of their proper end.