you can kill whoever you want. your stealth rating will just go down. anyhoo, if you look at your map when you're on the surface, there should be a building and a marker that says "place of interest" or something, should be right across from teh builiding the general is in. go in that builiding and climb the stairs to the 3rd or 4th floor and look out the window. you should see a room full of generals using your sniper rifle scope.