Some Tokyo politicians thought up the wonderful idea to "ban provocative visual depictions of characters who appear to be 18 or younger." Many speculate this comes at a time when Japan is facing pressure from other countries to curb its child pornography. I have a lot of problems with this.
To start, I don't care for these characters in anime. I would rather see realistic portrayals of women (such as Black Lagoon's Revy or RahXephon's Haruka) than the continually rehashed ideal of a naive, junior high school girl pining after a socially inept older man. That said, I don't necessarily think these characters drive fans to sexually abuse young children. Take a look at your average otaku's room and you'll find shrines to these characters alone rather than anything that suggests an interest in real little girls.
This ban is first of all an act of misdirection. As the author of this article points out, it's merely an "aesthetic bandaid" fix to the problem. Rather than take real, controversial steps to change the state of child pornography in Japan politicians decide to take on a safer target in underage anime characters in order to look like they're doing something. Authorities in Japan, whether in government or in business, favor the appearance of change rather than change itself, as you can read in this heavy, yet accurate rant.
Secondly, while it's a despicable decision politically it's also a dumb move economically. If this goes through it could injure Japan's anime culture, which is a major financial asset both domestically and abroad. As much as I may not care for the character type, there's no arguing that these "lolicon" characters have become a major pillar of the industry. Straight out banning their depictions would stop shows that feature these characters (of which there are currently a LOT), stop fans buying their merchandise, and cause the anime industry to shrink.
Finally, it's flat out censorship. Japan has not had a great history of fighting censorship, as their antiquated pornography laws will show, but it is censorship all the same. If no one is being hurt and there are people who want this kind of content, who are they to stand in the way?
Japan has a problem with fetishizing youth, but it's being sidestepped rather than dealt with by this solution.