Nobody should be paranoid of whether they should or shouldn't wear a costume because people judge upon that particular show.
I know this thread isn't meant to judge fandoms and for the most part everyone has been mature of this.
I belong into both Hetalia and Homestuck fandom greatly, it's just a part of my life. I can agree that several fans from Hetalia are irresponsible with flags and crude reference to dark times in history. There's a whole article about this shameful thing Hetalians did. However, that's only at most 30% of the fandom. Hetalia cosplay tumblr sites and the mature part of the fandom have actually been writing sections about proper care for flag and such. The stereotypical part...actually the whole show is pretty much disrespectful itself. If it's a story about countries in human form, of course it would be. It's just that the fans see it into a more comedic level and it's meant to be perceived that way.
Homestuck fandom is actually not bad at all. It's that 10% of the fandom that ruins everything. Part of which is because it is generally frowned upon because it's not anime. I've seen Doctor Who and Sherlock cosplayers in anime conventions and no one says much about it but to the Homestucks, people become unfair. *shrugs*
It's also just human nature to focus more on the negative aspects than on the positive aspects. If people just look more carefully, there are certainly more pros than cons in all fandoms.