The term biker
should be reserved for one percenters, members of outlaw m/c groups, their friends & affiliates. These are nasty people who trade in drugs, human flesh, & violence. Give them plenty of room; they consider themselves soldiers and are dangerous. Trust me, they still exist.
A motorcyclist is a "civilian" that owns & operates a motorcycle in a legal manner.
They're not as noticeable as they used to be but m/c's and gangs are still around. The ****'s Angels, Outlaws, Mystic 7, Nomads, Banditos, Pagans, & Mongols are among the most infamous and still quite active.
I repeat, they are dangerous people.
Mess with the bull, you'll get the horns, etc.