The slippery slope argument is always advanced in order to justify the status quo. The status quo is preferred by people who are more or less content with the current state of affairs.
Most resistance to change is generated by fear. Fear that things might get worse. As opposed to optimism that they will get better and embracing changes. Naturally, the people who prefer to draw from the deck are ones holding a hand that needs to be improved, and the ones that think they already have a winning hand will stand pat. The resistance to change crowd is essentially saying, "I got what I need, and I'm not willing to risk it just because your hand sucks."
I'm not just talking politics. I'm talking team mascot names - well okay that somehow has become political. Uniform redesigns. Corporate rebranding - I'm talking Mr. Peanut here not Mrs. Butterworth. People who are mad because a restaurant took something off the menu that they liked. Cars that drive themselves. New math. GMOs.
They don't understand any of it, they don't want to learn new ways, they are afraid they won't be able to function, they are terrified that something could go wrong. If it was up to those people we'd never have got answering machines, plenty of people were upset to talk to a recording. They didn't know how to handle it, they felt dumb not realizing it at first, they didn't know what to say, and they sure as heck didn't want to learn how to set one up for themselves.