In Christianity the most virtues deeds are those that have in mind the betterment of another, even if that means you have to take a loss or suffer pain to build someone else up.
The quest for human dignity is deceiving. It tells us we ought to be treated better. "I deserve better treatment than that." Pride always drives us to want to look great, or feel great about ourselves, at the expense of others. Jesus did not care what people thought of him or how they treated him, his greatest concern was honoring his Father.
In short, the Beatitude's relation to dignity is that it reveals to us that in God's eyes the demand to be respected or thought well of is a lesser known side of the human sin problem. Submission to suffering to make someone else great is viewed as normal behavior in heaven. But on earth it is viewed as abnormal and stupid. That is we have such a hard time swallowing passages like Matthew 5, our culture makes sin look normal and righteousness look abnormal.