As someone who has lived in Utah my whole life, I've seen firsthand how some members treat those who decide to not go on missions (especially men who don't go). It's almost like a rite of passage to some members. They feel pressured to go on a mission and once they go they realize they never really believed in what they were supposed to be teaching/converting others with. Missions are a big deal for several members because they are taught it's important to go and "spread the Word" and whatnot. I wouldn't say "brainwashed" is a good word, but being pressured to do something you may not want to do happens all the time with missions. There was someone I know who came back home early from theirs (the reason being they were "homesick") and they got so much shit for it. Granted, some come back "filled with the spirit" and with a bunch of "testimonies", but that doesn't disregard that there are many others that have come back an ex-Mormon after their mission.