While I do find lolicon and shotacon to be lacking in taste for me, I think banning them outright would place a hazardous situation onto fans of that aspect of anime. Much like hentai, eroge and other similar outlets, lolicon and shotacon provide a means by which fans of it can let out their urges without inflicting them upon any real child in real life. After all, Japanese society does place very high standards on conformity and respect for others which there are people who find it very difficult to adapt to unless they have some outlet to let out any violent and/or sexual urges that doesn't inflict harm onto others in real life. I believe banning anything like lolicon and shotacon would increase the likelihood of such people committing a violent or sexual act in real life as without an outlet for their repressed aggression, there will be a breaking point where such people can't handle the pressures of society any longer. There hasn't been any documented evidence that proves any lolicon or shotacon fans committing any real life crime against a living person. So as long as there isn't any such unbiased evidence behind this, I can't really support such a ban.