How to Refute the Slippery Slope Fallacy?
My first suggestion is to state the fallacy and explain it. I think that’s important in most circumstances. I think often people don’t realize they are falling into fallacious arguments. Once you’ve briefly explained it, I would recommend talking about moderation and how people every day all over the world restrain themselves thousands of times more often than not. Maybe even bring up how the person you’re talking to has restrained themselves in some way recently, perhaps by restricting how much they ate or drank, etc (might not work if they are obese or an alcoholic, but you get my point). For instance, I really love coffee, but I only drank 2 cups for breakfast instead of the 5 I could have easily consumed.