How do we differentiate a moderate person from a left/right extremist?

[RockHunter]

Left or Right...those labels are too generic to be really useful. They cover too many subjects.
One can be right of left on social or economic or hundreds of other subjects, and most people only accumulate various leanings rather than steer to one OR the other.

I find that those who whine the loudest about someone else being the extremist, is actually the extremist himself. When one side claims to be "moderate" or "center" yet uses terms like "far-left/right" or "extremist", that says a lot about the character and integrity of that side.