That was a pretty good story (I saw it the other day). The stunt described in the OP here is in blatant violation of the DC law, while the story you linked is about a guy doing something perfectly legal. I don’t think what they’re talking about doing would be legal if the guns were unloaded.
Another important point about what the Michigan father did. He put his own butt on the line without trying to get others to do the same.
How can it be in violation of DC law when any law contrary to the constitution; as explained in Maybury v Madison:
It is also not entirely unworthy of observation that, in declaring what shall be the supreme law of the land, the Constitution itself is first mentioned, and not the laws of the United States generally, but those only which shall be made in pursuance of the Constitution, have that rank.and the Constitution itself says that the right of the people to keep and bear arms "shall not be infringed."
Thus, the particular phraseology of the Constitution of the United States confirms and strengthens the principle, supposed to be essential to all written Constitutions, that a law repugnant to the Constitution is void, and that courts, as well as other departments, are bound by that instrument.
The rule must be discharged.