I'm not into Hetalia, nor do I have the will to watch it but I'd still like to put my two cents in.
The person who organized the shoot did warn everyone to watch how they act.
I WAS at Anime Boston and that Hetalia shoot was HUGE. They were located at the bottom of the steps outside the mall and I looked down when I was done with my Fate/Stay Night photoshoot.
It was a large crowd and they would not have fit anywhere inside of the convention center without being a fire hazard. The courtyard that is located outside but between all the buildings and more hidden because of the buildings was closed this year and that was the original location plan.
Now I know a lot of people are angry but something like this was bound to happen sooner or later. I don't support what they did. Merely explaing what I believed to have happened.
Now even though there were warnings to the group ON THE FORUMS, not everyone is on the forums. There are people who just hear about the photoshoot and show up.
Everyone is excited when there is a con, especially if it is 1) their first con, 2) the only con they attend a year, 3)They just are, with everyone hyped up and the adrenaline rushing, people tend to ACT BEFORE THEY THINK. We all know that this is a person's downfall in a lot of situations and it was in this one.
Now the thread on the AB forums shows us how sorry the person who put the shoot together felt, she apologized. Let her be now. She understands what happened but one person could not control that big of a group. People don't even listen to Staff and Security at cons, let alone another cosplayer. A lot of people may be like "Who are you to tell me what I can and cannot do".
It's sad what happened but it happened and the past cannot be changed. Let everyone learn from this and hopefully everyone can learn from this and the Hetalia community will learn and take a lesson from the incident.
Also this is not to be hating towards anyone so please do not take it like that. It is merely my opinion as I try to explain what could have happened in a logical way.