Just as an added note:
a. Some people make big deals out of nothing. They probably didn't see this as "a few silly cosplayers going too far" and more of a "Oh my god its Neo Nazis!!". In the public's eye.
b. Ignorance on flag respect... a lot of people just don't know you don't put flags on the ground
c. Hate the cosplayer, not the fandom. Just because a few Germany cosplayers messed up with the nazi slogans doesn't mean all Hetalia cosplayers are like that. I know i'm not... especially not THAT stupid o___o;;
Just throwing in my two cents since this thread happened to be revived.