Am I the only one a bit confused that they would murder people over the D only?
We have never seen them care that much about the D even with all we already knew about its meaning. They were never persecuted in the fashion Robin was.
For example, they had Garp, a D, working right under their noses and nobody cared. And no, the excuse can't be that he's a hero and overpowered, because he was a marine for decades before he became a hero, and the WG is supposed to have solid information networks. There was also Saul.