Because we actually believe in something. Most conservatives and liberals don't have a consistent moral philosophy so there is no point debating them.
I've been trying to narrow in on that consistent moral philosophy for various ism's. I'm not sure I've gotten very close in most cases except the general concept of tribalism. Every ism seems to be willing to bend the rules if it is perceived to be the common wisdom of the tribe.
An ever shifting mire of something which varies from libertarian to libertarian, all insisting the other isn't the real libertarian.