eric mentioned a very good point in his comment, about how difficult it is to assume goodwill in fundamentalist evangelism. i agree, it's difficult. but, it's not that hard to fathom why many of the rank and file may be meaning well with it. they believe that their specific religion is the one true path to salvation, and they want to get that out to everyone else--it's their responsiblity to witness, and save as many people as possible. a few are receptive. many are not. they see it as their duty.
still, i think there is a fundamental chasm between finding a deep responsibility to try and convert others to a faith, and reflecting that in governmental policy. they can witness on their own time. there is nothing preventing them from talking to people on the sidewalks, passing out tracts at the park, publishing letters in the paper, or posting opinion pieces on the internet. some may blow them off, some may stay to chat. if a convert decides that school should involve prayer or religious teachings, the convert can put their child in a religious school, or attend a religious college themselves. the convert can decide to live a life in accordance with the religion's tenets.
but, it hardly seems consistent with the idea of freedom of religion to pass the buck to the government, to work to get the government to do a forcible version of witnessing for that faith. it's impersonal. it infringes on the rights of people who decide not to listen to those who say that evangelical christianity is the one true faith. a separation between church and state does not prohibit evangelicals' free exercise of their faith--up to and including large-scale witnessing projects. the only thing it prohibits is an overlap between the church, the instrument that works in the interests of its faithful, and the state, an instrument that ought to work to protect everyone's interests as best it can.