One of the most admirable things about the Democratic Party, in my opinion, is its openness to anyone who wishes to join the party, and its open-mindedness toward new, even old, though controversial ideas. Until recently even Conservatives were welcome,; and I certainly understand the antipathy towards anyone with the audacity to identify himself as Conservative given the rhetorical vitriol and open hatred spewed forth by Republicans (actually by those in the Republican Party who falsely, in my opinion, identify themselves as Conservatives; previously as Neo-Conservatives --- Neo meaning not really).
There is, however, in the Democratic Party a Liberal element who would like to see the Party purified. There is this element also in the Republican Party. They call themselves the Tea Party. The problem with purification is that it leads to obsessive behavior and unrealistic expectations. I have noticed this tendency over the past few years also in elements within the Christian Church calling themselves Evangelicals (I would quickly point out that this is not true of all Evangelicals, but it does seem true of the vast majority. I am deeply religious and have Evangelical friends to whom I consistently contend that sanitizing the Church Satinizes it --- justifying them in doing really reprehensible things.
I say all this because I seem to sense a tone of contempt in your request, but it does, of course, require an answer.
A basic premise of the Conservative Movement is If its not broken, dont fix it. This, of course, creates the problem of discernment, a problem with which Liberals have confronted Conservatives with for very a long time. How do you convince a Conservative that something is broken? The answer is, You cant. This is something about which a Conservative must recognize pretty much on his own, but once recognized as a problem, he will do everything in his power to fix it.
This brings us to the value of Conservatives. They are slow and they are obstinate (and far too often arrogant), but they are really good at making things work, partly because they are slow and obstinate (the arrogant part has questionable value).
I can expound further, if you like.