The church is to regulate, teach, and dictate culture. But this can only be done effectively after we have been sure we've done everything we can to clean-up our own "church" houses, first. The process goes this way: let us look to our own individual (local) churches, then to our presbyteries, and then to our denominations.
After we've done what we can there, we go to the broader church. You might be wondering, "How do we do this 'clean-up,' especially since there are a lot of messes about, and some of them are centuries old?" Good question. First of all, where we actually have power and jurisdiction, we must use it. (This is the case in our own church denominations, for instance.) Then, where we do not have direct power and jurisdiction, we employ words of instruction and admonition (with as much understanding and grace as possible--especially in the initial stages).
The church needs to be governed by the Puritans among us. They are the ones with the courage and the doctrinal goods to go after some of the most public, scandalous, (and pernicious) errors first, like the ordination of homosexuals, etc. Again, since most of us are not operating under those (more liberal) denominational structures, we must do our work "from afar" (as it were), with words. (Where we can personally interact, that is good, too.)
The entire church does not need to be *completely* straightened-up before we begin addressing the non-churched world, (or else, we would never get started at all)--but a sincere effort must first be put forward.