Arguing from an extreme case to get a principle is what people always do, on both sides of any argument like this. When people were trying to change the laws against abortion, that's just how it was done. Nothing dishonest about it. If you are in a fight you go for the opponents weak point.

That isn't necessarily to say battling things out is the best way to work out how we should conduct our affairs.

In a less belligerant mode the equivalent thing is to try to find some area where you and the person you are debating/negotiating with are actually in agreement. Then you maybe try to bring them to see that there is an inconsistency between this area, and some other areas. And no doubt the other person does the same to you.

And that is what I had in mind in my opening post in this thread

"Pick any country in Latin America" that way of talking is getting close to throwing bottles. It asks for a response in the form "Only in America would so and so happen". (And I won't say what "so and so" is, because it could be a lot of things, bad and good.)