First, it continues the notion that the DFC and the Democratic Party are adversaries, or even distinct entities. In particular, it continues the notion that there is a monolithic Democratic Party with which DFC would negotiate. And that doesn't even get to the planks that I think are ill-advised. My understanding of the genesis of the DFC platform is that it was developed by folks with relatively little direct experience in City government. Or someone with some experience in municipal law could have warned them of the provisions that are illegal.
Platforms are relevant, if at all, during campaigns.
They serve two purposes. The first purpose is to let the Party make a statement on a matter of principle. Aside from David Duke in Louisiana, I can't think of it happening too often. And, as we saw in May, we don't really want to do it anyway. DFC and the Democratic Party are not adversaries.