In the 60's we were refereed to as rockers and it then became greasers into the 70's. I don't remember anyone who rode a motorbike differentiating between types of rider except the mods on their scooters. Half of my mates were rockers and the other half were mods. We all new each other but would only ever meet up at certain places which were common ground. The greasy spoon cafés were very much a no no for the mods and we kept away from Wimpy bars. It is a by gone era and for me those days are gone, great fun at the time. The term biker was never used then and I am not sure when it really started.
As to choice of clothing, wear what you feel comfortable and safe in and except what others want to wear.
I do know that people who ride motorbikes seem to have what I can only decibel as a brotherly/sisterly way with each other. You may be riding alone at times, but you are never alone when out on your motorbike. Another rider will always approach you and talk and not necessarily about bikes. There is more often than not someone willing to help.
When I was out on Sunday I got a nod and a thumbs up from a motorcycle cop, which I thought was brilliant.
What more could I say, people who ride motorbikes are a great bunch of people