what is a false dichotomy? can someone explain it? for the life of me i cannot grasp the concept. does it mean something that appears more complicated than it is? if not, then what is a word for that?

I'm wondering if there are good examples where an arbitrary distinction between things is useful and moral and how you would respond to those who dosagree. If you can't define where the line exists then should there be any distinction made to begin with?

Examples: what we consider a species, the line between adults and children, the rights of an individual vs the rights of society. All of these are arbitrary, but important.

Effectively, what approach would you take to someone who says that two things aren't different because you can't define the exact point where one becomes two. I understand this touches on many different philosophical question (Ship of theseus for example) and I have a sense that there is some sort of underlying assumption or complex question that is being leveraged to obfuscate the fact that its practically impossible to come up with definitions that encompass 100% of cases and if we dont distinguish between things and concepts then discussion becomes untenable, but can't put my finger on it.

I remember hearing someone make an analogy and the other guy called it a false dichotomy, that brings me skepticism to every metaphor I ever heard because more of them could be false dichotomies.