The reason is because cuteness and innocentness are seen as something sexual for those westerners and not something adorable and have to be protected like for us Asians, childrens are mostly look cute and innocent while those westerners rarely can find it on their adult western peoples.
For reference including evidences just go to http://antiwesterncosplayers.tumblr.com/post/82679952150
I wonder if those westerners also see our Anime as something sexual because our Anime main attraction are cuteness and innocentness, I have seen some westerners who said they hate our Anime by accusing our Anime as pedobait stuff. No wonder Japanese not chosing any westerners to form the sister group for AKB48 and instead chosing other Asians, just like our Anime AKB48 main attraction are also cuteness and innocentness so forming AKB48 sister group in the west will only get it to be labeled as pedobait group in the west by those westerners, aside from the fact that westerners are not cute.
May this knowledge help in reducing the number of pedophile victims in the world especially in the west. Don’t forget to reblog this to make the western authorities become aware about this so that they will come up with an effective measure after knowing the real cause to prevent more victims.