One of the more common logical fallacies is the slippery slope. Bad event A could lead to Worse event B, which creates Catastrophic event C. While it’s a possible chain of events, it leaves out any consideration of the likelihood. This is a fair critique of many things, because generally A doesn’t lead to B, much less to C.
Misapplying the Slope
But it doesn’t apply to many arguments as much as people say it does. It’s convenient to apply a claim of “slippery slope” to a train of thought that someone doesn’t like, but it’s not uncommon for those doing it to leave out context, counter-examples, and past events to support the original alleged “slippery slope.”
Leaving Out Context
The more common word for this is “cherrypicking.” Essentially, the counter-argument makes their case against the slippery slope by finding the least causal parts of the original argument, only mentioning those, and of course dismissing that ridiculous logic. In a sense, they’re straw-manning.
Leaving Out Counter-Examples
This is really similar to leaving out context, but is specific to illustrations and examples.
For instance, if someone argues that “marijuana is a gateway drug,” then provides two anecdotes (which are weak evidence) and a clinical study in support, someone wanting to claim slippery slope quickly will simply ignore the study and hammer on how weak the anecdotes are.
Leaving Out Past Events
This is the most egregious way of falsely claiming slippery slope. Rather than consider the past events that the argument is relying on, the counter-argument starts from the very last (or close to last) event and claims there isn’t enough to prove there’s any slope being descended in the first place.
For instance, the “social justice” phenomenon was merely cute a decade ago, all the rage for some people on tumblr three years ago, and nowadays seems to dominate the entire “social progressive” scene. Saying that it’s likely to take over the entire messaging of liberal politics isn’t an unsupported thing to say.
But someone noting that what was a very short time ago a radical approach to public discourse has gained too much influence too fast could be shrugged off as “not alarming” since “social progressivism has been around for decades.” Notice how the progression of social justice in specific was dropped in favor of talking about what it has taken control of.
Arguments From Extent
To “combat” the slippery slope, too many make the reverse error of claiming something isn’t as bad as it could be, thus the argument is totally invalid.
To visualize it, this line of counter-reasoning is like arguing the slope isn’t as steep as the original argument, without doing anything to dismiss that there’s a slope one can descend in the first place.
Of course, this is absurd, but the words “it’s not that bad” or “it could be worse” have far too much mindshare in debate. To even say these gives the original argument merit (which it may indeed have) that the person countering likely doesn’t mean to give it.