In The Guardian, I read the following passage
The former Leicester, Everton, Spurs and Barcelona striker, also vowed to continue to “speak up for refugees and immigrants and British values of tolerance and free speech”.
The [Daily Mail] article devotes 17 paragraphs to recounting what the rightwing newspaper calls Lineker’s “leftwing take on global politics” and “oh-so right-on views” before first mention of the 55-year-old presenter’s alleged tax affairs.
It seems that in British English, the expression "right-on" is used to mean:
(chiefly Britain, often pejorative) Possessing political and social views that are considered to be fashionable and left-wing.
However, how did this phrase come to have this meaning in the first place? IMO there doesn't appear to be such a clear link between the original expression "right-on" and this pejorative meaning.