If people are twisted enough to like really oversexualised minors in sed sexual way, that's not good.
If the laws to prohibit this also end up constricting production of anime for those who are not like this, that's not good either.
I suppose we'll just have to wait and see how this turns out.
Let me make a favorite counter-example. Do you think only twisted people are fans of shows like "Buffy The Vampire Slayer"? Now, keep in mind this is a mainstream show that was massively successful and made Joss Whedon the celebrity creator he currently is.
In "Buffy" we had a 15 or 16 year old girl getting it on with a 30-something (actually hundreds of year old) Vampire as a major plot point. Remember this all happened while she was in high school and there was time for him to turn evil, be defeated in a season finale, return with a soul, be kept locked up by her as a beast for a while, leave for his own spin off season, and then make a return apperance for another season finale when Buffy was finally graduating High School. I don't know for sure what age she was off the top of my head, but she sure as heck wasn't an adult.
The reason why "Buffy" is considered acceptable is because it's a work of pure fantasy, real girls are not like Buffy who is a super hero. Our real world morality doesn't easily apply to a situation like that, if we had real super heroes our logic in dealing with them in situations like this would be differant. I mean if the fate of the world can rest in your hands periodically, you can probably determine when you can go to bed with someone on your own.
I also look towards movies series like "Porky's" and "American Pie" as other examples. Like it or not, teens having sex is part of growing up and learning about life. In general I tend to only have issues when you have adults having sex with kids. I'm one of those people who feel teen on teen stuff is fine if done responsibility, and one of those guys who feel that the proper thing to do (especially seeing as we won't ever stop it) is to distribute condoms and such and put more of a focus on safe sex, rather than trying to force hard core abstinance. Of course this doesn't cover the Buffy thing (Angel was not a Teenager), that falls under fantasy as I explained above.
The thing about this law is that it's not going to affect any of the really creepy stuff that people mention as being what Japan needs to clean up. That isn't what this law does. Those works are still defined as pornography. Urotsukidoji, La Blue Girl, Queen Of Darkness, Bible Black, and other well know titles are all adult rated porno over ther just like here. As long as they keep that rating and continue to be distributed as porn, nothing changes.
What this law actually does is targets fantasy series, things like "Buffy The Vampire Slayer" where you might have sexy teenage super heroes of one sort of another carrying on relationships during the series. The arguement that a 15 or 16 year old Buffy-type is too sexy and should be illegal even if there is no hardcore porn actually involved.
In general, the main run of Anime doesn't get much worse than the general run of comics books in the US. A lot of T&A, and some implied sex going on behind the scenes. People who complain about this stuff in anime are pretty naive about media in general, and even what is permissable within a "T"/"PG-13" rating given how few producers push the limits properly. Some might remember that in the "classic" movie "Scream" there is even a joke made about this where the protaganist's boyfriend wants to have sex with her, and says "no, but I can give you the PG-13 version" before flashing her tits as one of many self-aware jokes. The point is that what is being actually targeted are things that have been within permissable limits in both Japan and the USA for years.... again as I pointed out, the way this law seems to read, the stuff that pushes the limits and makes Japanese animation infamous is going to be untouched. As long as they keep slapping that adult rating on the DVDS, Tentecle Rape is going to continue to thrive. People who seem to think hard core hentai is released on TV for children over there, are really uninformed about Japan, right up there with fanboys who go in the opposite direction and seem to think adults in Japan prefer to read Manga over newspapers and knowing what is actually going on in the world/their area.