@ETpro Yes, I know where the names came from; and strictly speaking, the names weren’t very informative then either. It was a matter of convention then, and it is a matter of convention now. In both cases, background knowledge is required to understand the reference.
I’m not saying that “regressive” isn’t the proper counterpart to “progressive,” just as “reactionary” would be the proper counterpart to “radical.” But since reactionaries are more extreme versions of regressives and radicals are more extreme versions of progressives, it is useful to have directional terms that capture what they share.
“The right-wing” includes both regressives and reactionaries (as well as right-leaning moderates), while “the left-wing” includes both progressives and radicals (as well as left-leaning moderates). These are useful terms to have, even if they do not address other complicating issues.
In any case, I’m fine with calling right-wing extremists “reactionaries.” But as “the right” does not only refer to extremists, it seems to me that “the right-wing” is the most suitable replacement term.