step-kids and step-parents

I have been married for three years in my second marriage to a guy who's 17 year old son is the laziest, unhygienic, most arrogant, selfish, ignorant know it all person I have ever had the chance to meet. My husband just is completley ignores his behaviour or should I say is not willing to tackle the issues that are becoming major family problems.
I Know as parents we can all be biased towards our own off spring but I also have a 17 year old daughter who is the complete opposite, she the sweetest most helpful and respectful person I know, I am not saying she is an angel all of the time because she as her faults just as we all do. My gripe is that when she steps out of line or does something that irritates my husband insists on her behaviour being addressed and often reprimands her or puts her down in front of other family members. I feel that there should be such equity and that both kids should be being treated, when I have tried to line my stepson out my husband treats me like I am his worst enemy.
I feel like he points out and makes a big deal of he misgivings to mask the many problems that his son is creating, at the end of the day both kids should be abiding by the same rules of the house and that is not happening.
My daughter knows that there is a vast difference in the way they are treat and her self woh and moral becomes low at times, I try justify what is going on here to her but I feel she is emotionally immature to handle this issue and should not have to be doing so.
I try very hard to treat them both the same despite my hatred of my stepsons behavior but I am recently starting to resent being nice at all to my stepson mainly because of his behavioor but also because he as no parental guidance and I am not allowed to offer it!
I am frustrated with the whole situation and angry at my husband whom I feel needs to wake up and see how his treatment of both kids is affecting them and see the kind of adult his boy is going to become. My husbands parents act exactly the same way as my husband with both kids, even though everyone else can see exactly where the favoritism lies. Any advice?