I can tell you exactly how serious it was to be perceived as pro-German and sympathetic to the Kaiser during WWI. I have the copy of an 1918 A.P.L. report of an investigation of my great-grandfather about an accusation made by a co-worker that he was pro-German and 'in the habit of voicing himself in a disloyal manner'. It's titled "Alleged Disloyalty and Seditious Utterances...European Neutrality Matter'. Apparently my grandfather had made statements like, 'The Kaiser is as strong as the rest of us.' Nothing came of it. All especially surprising because he was born in the U.S. (his German parents immigrated to the U.S. in 1854) and his son - my grandfather - was a Lt. in the U.S. Army. So it didn't take much.