people changing.

So I have come to realize that soo many people change, for the better or worse i haven't decided that yet. But in a very different direction then they use to be in. 
i have 2 very good friends here or well i thought they were. but maybe people change and grow apart from there closest friends because they don't believe they are acting the right way or made a couple bad decisions. but is that right? to leave your closest friends behind because you think what they are doing is wrong? or should you stand by them and be a friend to them no matter what? There not breaking the law but there going to end up breaking up there families. they think its ok because there doing it with woman and not doing it with another man so its not actually cheating. (there words not mine)
But i think its very wrong! they asked me if i wanted to join in what they were doing and i got soo mad at them that i just left the restaurant we were at and went home. 
 How can someone be soo against it earlier in the year and then change soo fast and think its perfectly fine to do that. and to even ask me to do it when they know it would just break up my marriage! how can someone people be soo selfish and destroy there marriages over sex?? i don't understand it! is there no value in being married any more?
 people around here jump from one marriage to another like its a kids favorite color changing every week because there new toy is that color! its ridiculous! i don't know if its like this every where but its really starting to make me question if we should stay in the military or not. i don't want my kids to be raised in this type of community thinking its ok to cheat on your husband or wife. and have no respect and no value for being married.
Being married is suppose to be secrete and have meaning to it. people are suppose to be with that person for the rest of their lives and not want to have sex or want be with another person! if you don't want that then why are you still married? Your just going to hurt the people close to you and end up with nothing.
people say im old fashion here because i respect my husband and i dont check out men and dont think about or fantasize about being with a man or a woman. But i dont think im old fashion i think what there doing is wrong. your suppose to be with the person you married and have respect for that person to not do any of those things.
i dont know im really torn between staying there friend and just letting them go there own way and leave there lives right now.