The following argument will strike many as trivial, which is precisely why I have sandwiched it between what I believe are two more essential points. Nevertheless, having disposed of the notion that Christians are obligated to construct a moral society through legislation, it is important to look at the consequences of continuing to attempt to achieve such political ends. Admittedly there is a real sense in which Scripture acknowledges that that to be a Christian means to open yourself up to ridicule. Paul even accept that the world will always look down on the wisdom of God, ironically labeling it folly. Nevertheless, it is important to distinguish between opening ourselves up to be mocked and causing God to be mocked.
You are the light of the world. A city set on a hill cannot be hidden. Nor do people light a lamp and put it under a basket, but on a stand, and it gives light to all in the house. In the same way, let your light shine before others, so that they may see your good works and give glory to your Father who is in heaven.
Aspire to live quietly, and to mind your own affairs, and to work with your hands, as we instructed you, so that you may walk properly before outsiders and be dependent on no one.
Jesus and Paul agree here on what ought to be a self-evident truth: people are watching Christians and what they see determines what they believe. Christians individually probably are not to keen on the notion that their lives are under a microscope, and why should they be? God is more than fully aware that we all still sin. Christ is the image of the perfect human, not me. Nevertheless, the corporate behavior of Christianity speaks volumes to the world, particularly given how loudly we shout about certain issues. Unfortunately, what we're shouting about isn't meekness, poverty, righteousness, purity, peace, and mercy as in the Beatitudes--which precede the first quote--nor are is the public face of Christianity brotherly love, quiet living, and industriousness as in the passage from 1 Thessalonians. What are the loudest messages about God instead?
And if that seems like an extreme example to you, there are certainly others. Look at the now infamous statements of Richard Mourdock: "Even when life begins in that horrible situation of rape, that is something that God intended to happen." Frankly, I don't find that sentiment all that appalling, not because I agree with it but because I know it represents a large and historic branch of Christian theology. The popular media and the vocal critics of Christianity are less philosophical about it. It is sentiments like these given voice only because they are attached to political power: constitutionally challenged and protected protests or theology spilling into public policy. Meanwhile, I could walk into work tomorrow morning and proudly declare that I believe therapeutic abortion (i.e. abortion to save the life of the mother) is wrong--and I do believe that--and no one would bat an eye. They know that I have no interest in launching Christian ethics into the public sphere and so derision is replaced with apathy.
Meanwhile, regardless of what I believe about abortion--which is made largely irrelevant by my theoretical lack of a uterus--I would hope that when people describe me it is in terms more personal and therefore more sympathetic than the way most people choose to describe Mourdock or the Westboro Baptists. Those groups exist only as their public faces, only insofar as their behavior has consequences on a political scale. Yet when people interacted with Jesus, he specifically rejected any reduction of himself into a political persona. He was a healer of the sick, a feeder of the hungry, and a forgiver of sinners--not to mention a man of indisputably impeccable character himself. Richard Mourdock may very well donate to food drives. He may volunteer at hospitals. He may forgive any and everyone, even rape victims who get abortions. It's irrelevant. He will always be that Christian who thinks God is a rapist and wants to write laws on the basis of that belief.
It is time for Christians to take a long, hard look at just how extensively our involvement in democratic politics has opened us and, much more importantly, God to ceaseless ridicule. By allowing the public presence of the Christian faith to be reduced to its political manifestation--either is moralistic bigotry or socialistic coerced charity--we have transformed God the Father, Son, and Spirit from persons to partisans. There is no rehabilitating Christianity's political image. It is not possible to offer to the world a kinder, gentler, truer Christianity that will make the faith politically palatable. God makes radical ethical demands of His followers, and libertines are never going to be okay with that. God makes radical social justice demands of his followers, and aristocrats are never going to be okay with that. As long as the faith is married to political agendas, it will never be anything more than a caricature of the truth which Jesus came to impart, a revolutionary practical, ethical truth. In the meantime, more people are likely to disassociate with Christianity in favor of some vague notion of "spirituality" because to be in church means to be Richard Mourdock, et. al.