You are not supposed to take pictures in Arlington.
Incorrect. I have done a good bit of photography at National Cemeteries. You are not supposed to take photos or film anyone obviously grieving, and should always ask permission to take a photo of anyone graveside or of a burial ceremony (Jesus Christ, I would never do that). While these rules are set for media, everyone absolutely should abide by them and respect them, it's the right thing to do. 99% of the time this has never affected me, as I photograph older historical graves, there's no one there. I enjoy visiting any cemetery with older, historic graves, and make it a point to do so when I travel.
You absolutely are not supposed to do partisan political shit in National Cemeteries. That includes photos and videos for campaigning. This is all National Cemeteries, not just Arlington.