I think that most Early Rock and Roll artists such as Little Richard, Elvis Presley, Jerry Lee Lewis and Chuck Berry were considered rebellious because they would generally act differently on stage during they're performances then other artists at that period of time. And they would most of the time dress more "unprofessional" then others such as not wearing suits while they would be performing (like how Elvis wore Jumpers etc).
What would those same performers have to do to maintain their rebellious reputations today?
There is really no set stereotype for perfomers/musicans in today's society as there was back then. And there is so much more different genres of music today that everyone basically sets their on individual style. So I'm not really sure how I should answer this question.
"Does Elvis Presley deserve the title of “King of Rock and Roll”? What about Bill Haley or Chuck Berry?"
I think that Elvis deserves the title because no other Performer has ever moved and has been able to do so well between the genres of so many different kinds of music. Such as Rockabilly, Country, Gospel, and R&B (And also has been recognized as an idol in each). And also he has had the most Platinum Hits, most Gold Hits, etc.
(Plus Nathaniel was born on his b-day, lol)
How did the race of performers affect their popularity, or did race matter to most fans?