The question was put: "[In light of the LDS Gospel Essentials Manual which says], 'Chapter on Law of Chastity. Satan attacks the standards of modesty. He wants us to believe that because the human body is beautiful, it should be seen and appreciated. Our Heavenly Father wants us to keep our bodies covered so that we do not put improper thoughts into the minds of others.' Is it my responsibility to ensure that another person does not sin? and to what degree should act to prevent another person from sinning?"
To which I responded:
1. To answer your direct question: yes, we all have a responsibility not to conduct ourselves in a way which causes or encourages others to sin.
2. That said, the example you have cited from the Gospel Essential manual embodies some assumptions and positions with which I strongly disagree. First of all, I think we should leave Satan out of the equation and try to look at the issue as objectively as possible. The minute we decide that Satan wants "X", then the rational debate about whether "X" is OK or desirable tends to cease in religious circles. The given rationale for why "Heavenly Fauther wants us to keep our bodies covered" is "so that we do not put improper thoughts into the minds of others." This in turn assumes that sexual thoughts are (a) inherently wrong; and/or (b) likely to cause us to commit sin. We should face the following facts: (A) Sexual thoughts are a natural, inevitable, and acceptable part of our brain's activity which arises out of our inseparable sexuality; (B) The overwhelming majority of the population (apart from people with mental disorders) possesses the ability to separate fantasy from reality, and sexual thoughts or fantasies about someone do not mean that we will attempt to have sexual relations with them (although I certainly concede that people generally won't pursue a sexual relationship if they at least haven't thought about doing so); © masturbation is a safe and acceptable outlet for sexual fantasies, which can have the benefit of reducing the longing associated with an unfulfilled fantasy, and thus reducing the temptation to act out the fantasy in real life; (D) anything less then separating males from all female images will still leave male sexual fantasizing in tact. Attempts to eliminate sexual fantasies through what has been termed "modesty" tend to either be ineffective half-hearted efforts, or else cause greater problems than they solve. In some countries, women are oppressed by having to wear burkas, the rationale being that it is better for them to cover themselves completely and be virtually excluded from the bulk of public life then for men to have sexual thoughts about them. In fact, it seems that rape and abuse of women are more common in societies which try to suppress sexuality and sexual expression than in more sexually liberal societies. Perhaps there is an unintended heightened sexual allure about the mysterious unseen which drives men to seek sexual release in much more dangerous ways such as coercive sex. I highly recommend that anyone who disagrees with me on this point broaden their education on the subject, including watching the movies "Osama," "Kandahar," and "The Kite Runner". (E) beating puritanically driven standards of modesty into our young women will likely have some additional unintended side affects, including causing them to feel less comfortable and secure about their own sexuality, and creating mistrust and guilt about their sexuality even once they are married.
In my opinion, there is a place for the principle of modesty. But the driving rationale should NOT be the prevention of sexual thoughts and fantasies; it should be for the reasonable functioning of institutions, to reasonably prevent unwarranted distractions from what needs to get done. For example, it probably would not work for everyone to show up to a sacrament meeting in speedos and bikinis. It would disturb the mood of the meeting and make it more difficult to concentrate. A similar principle applies to children in school. If kids are too scantily-clad, it can interfere with the academic environment which should prevail. But we should dispense with the notion that sexual thoughts are "immoral". For generations, parents have not grasped or appreciated the problems caused by trying to suppress their children's sexuality. Furthermore, the suppression of sexuality leads to a great deal of dishonesty. People find themselves in a position where they hide their true thoughts, feelings, and behaviors in order to fit in socially. If it is a sin to cause others to sin, then perhaps we ought to take a very hard look at the dishonesty we are encouraging by having unjustified and unrealistic expectations when it comes to managing human sexuality.