Politics are divisive enough as it is. By labeling somebody as “a liberal” or “a conservative,” you assign a set of beliefs and opinions on practically every issue imaginable. We all know people are more complex than that. One can hold mostly liberal views, sure. Or hold conservative views on some things and liberal views on others.
But using these adjectives as nouns only serves to lump everybody into one of two opposing absolutes, which shuts down any thoughtful debate and widens the “us vs. them” divide.
We’ve (mostly) moved beyond using other adjectives as nouns; we rarely hear anybody referred to as “a black” or “a gay” anymore. Why not do the same for liberal and conservative?