You know better than that. islam STILL stones women today, you had to go back to the Old Testament to find the stoning of women being practiced.
You can't pull arguments from a thousand years ago when comparing it to islam of today.
You don't have to go back that far to find significant punishments for adultery (not sure what punishments extended into the 20th Century in this country, but certainly many extended well into the 19th). While I'm not suggesting that we go all the way back to stoning, I do think that the increasing acceptance of adultery has been very harmful to society.
I don't think that complaining about Muslims' following parts of Mosaic law that Christians ignore is going to be very productive. Muslims could quite reasonably argue that if Christians aren't going to follow the law they should strike it from the Bible; if they're not going to do that, they shouldn't complain when someone else follows the law.
I think there are many better issues with which to question Islam (e.g. why was Mohamed excluded from some of the sexual laws that applied to other people; isn't that awful convenient for him?) I'm not really familiar with the Quran, but if one is going to complain about the messages therein, I would think one should focus on those which differ from the Bible.