Actually, there's plenty of acceptable reasons for it to be so. 1. Many believe (myself included) that the "Jedi way" was flawed, and that the "no attachment" rule was one of those flaws. 2. Luke isn't the same kind of Jedi as the Jedi of the old order, and it's totally believable that he would create an order that was different from the old. 3.Dogmatic adherence to a philosophy without any room for growth is a bad idea. It usually leads to problems. Flexibility is key for things to keep from being stagnate. 4. Luke was raised by a family, and still has a sister. It's believable that he would value these connections and not teach against them. 5. Anakin didn't fall to the darkside because he was married, he fell because he was a selfish, power hungry, jerk. He was like that before he was married. 6. Luke has already disproven many of the rules of the "Jedi Way" already. Raised by a family, taught after he reached adulthood, strong emotional ties with friends and surviving family members, etc.