During the 70s the LDS church got caught up in a wave of end time talk and became much stricter ( my mum wouldn't drink coke or buy sweets called wine gums in case she became addicted to caffeine or got a taste for alcohol by taste association ) especially regarding sex and music ( reaction as well to the era!) but it's gradually winding back those elements to a more 'do what you want in the bedroom' approach rather than 'sex only for kids and force yourself to find it icky while doing it' default.
Perhaps the people you knew only started to pay attention to these things during the 70's, but they have been a part of Mormonism since the early days. A quick search of the Doctrine & Covenants reveals that preparation for the Second Coming of Jesus Christ was always taught as important, and this is scripturally connected to what many refer to as the Apocalypse, or a destruction that precedes it. The health laws which condemn harmful substances are contained in the Word of Wisdom (D&C 89). They were revealed in 1833 and never changed. It is true that there was a special focus on music during the 70's, and that probably did follow the concerns of the general culture, but they were not, however, unique to the era, as LDS Church leaders warned about the content and effect of popular music much earlier than that. LDS scriptures also make a distinction between good and bad music.
There is a tsunami of intellectual disaffection within the LDS church right now that is breaking it from within.
This claim is false, according to available data from non-LDS sources:
"Many Latter-day Saints, however are finding answers that confirm and renew their faith, according to research conducted by the Pew Research Center’s Forum on Religion & Public Life for its landmark "Mormons in America" [PDF] study last year. A significant majority — 77 percent — of those who identify themselves as members of the LDS Church "believe wholeheartedly in all the teachings of the church." That number is higher among respondents who have attended college (81 percent), and even higher (85 percent) among those who are college graduates.
Some Latter-day Saints, however — 22 percent in the survey — find that "some teachings of the LDS Church are hard for me to believe." That number declines as individual educational level increases." [Source]
See also, Latter-day Saint Social Life: Social Research on the LDS Church and its Members, edited by James T. Duke, especially chapter 9: Secularization, Higher Education, and Religiosity, which presents similar findings.
It is so blatantly untrue ( historically) that increasingly the core members admit they stay because even if wrong its still a very safe and fulfilling lifestyle…
Two problems here.
1) It is absolutely false to claim that the LDS Church is "blatantly untrue ( historically)." In fact, there is much to support its claims, some of which was laid out about 60 years ago in the book (which you can read online), An Approach to the Book of Mormon. There are many more places you can go for evidences supporting the Book of Mormon, and I have provided several in my response to the Awake magazine. You have to do your homework instead of merely making unverifiable claims.
2) It would be ridiculous to stay in an organization you believed was wrong, though I realize there are some who do fall into this category you describe. How "safe" is a false organization? Just ridiculous. If you still believe in God, go find out where He wants you to be!
Just trying to keep people honest here. The worst kinds of arguments are those based on false information. Don't want to be Mormon? Great. Just don't go around telling lies about us, intentionally or otherwise.