ok I think II get it. It's about optics. If POTUS and team went after them it would look like a political hit job, but by them investigating him, they have opened the door to allow POTUS and team to investigate them back. In terms of war (or a house invasion) if you attack your enemy first, or attack the robber outside your house that's just watching then you're the bad guy. But if they attack first, or if the bad guy come though your front door, it's free game.