You are offereing a straw choice, and perverting time or ignoring the passage of time in your shallow facile little analogy that is flawed nine ways from Sunday.
But to answer your poorly structured scenario, they should have fought to keep their party from becoming Stalinist. I would imagine some of them did. In the meantime, I suppose they voted mostly for that party. Of course, by “old school” Democrats you mean Reagan Democrats or even future Republicans - meaning they hand a natural landing place to jump too from the Democrat Party.
Thus, your analogy does not apply to this situation in any way, shape or form, but nice try. So no, don’t even try to pigeon hole “my perspective” into such a straw argument.