In all sorts of debate, the ‘slippery slope’ argument is common. It takes this basic form:
- My opponent wants to do X.
- I think that will inevitably lead to Y, which I think is undesirable and probably unpopular.
- Therefore, we should not do X.
For example, see claims that granting equal rights to consenting same-sex adult couples would mean we need to allow pedophilia.
Not only must the onus be on the person using the argument to explain why the posited progression is inevitable. They must also explain why the ultimate outcome is undesirable. The whole argument type is a bit questionable, really. It saves those opposed to X from having to explain why they oppose X itself. It is easier to oppose free lunches for malnourished orphans because you think it will lead inevitably to godless communism than it is to oppose it on its own merits. It is easier, perhaps, but often not convincing when you think it through.
Slippery slope arguments are often a smokescreen intended to cause confusion. Alternatively, they are a last ditch defense when all better arguments have been convincingly rebutted.