I don't believe it's okay. I just believe it's constitutionally protected.
shielding himself from potential assassins.
That is not shielding from potential assassins. It's about keeping contrary views out of the public eye as much as possible.
Actuallly the media try to keep President Bush out of the public eye, electronically, as much as possible. The only way he gets his message out is in face to face meetings, and he is at risk of a kook killer every single day.