Rebel: a person who rises in opposition or armed resistance against an established government or ruler.

But also


(of a person) resist authority, control, or convention.
show or feel repugnance for or resistance to something


So by definition the "Rebel Flag" as it were, could be seen as anti-establishment, counter culture, etc. which was the case when Billy Idol was rocking it.



The Dukes of Hazzard, they were anti-establishment/anti-Boss Hog and corrupt Sheriff Roscoe P. Coltrane......but nah we can't have that see...we must comply

....that was in the 70's and 80's where people were using that flag as a political statement to be against the status quo.