It seems to be a map of people ( who have protective orders against them and who own guns. )
not people (who own guns) and people (who have protective orders against them)
There is a big difference there. I think if they were mapping gun owners there would be a lot more dots, especially in the western part of the state.
But that is not the main issue. The point is that there is a database of gun owners in MD they check the people with protective orders against.