The Urban Myth is just what the name says it is, a widely believed perception that is not true. Urban means a large population or dense population, essentially implying a majority of people. Myth means false. This is not the same as an Urban Legend. A legend is not necessarily false. A legend has a historical basis and is not provable. The bar for falsehood is set higher for the term myth than for a legend. If we want to emphasize that a widely believed narrative is false we would use the term myth not legend.
Political Correctness is a similar concept. It suggests that a widely held belief is actually false. There is a belief that political correctness is an antithesis to democracy but democracy can be unfair, subverted, hijacked and manipulated. The will of the majority is not just a majority of people but the force of collective rule which includes not just elections but demonstrations both peaceful and violent. It even includes political assassinations. Democracy also requires the tolerance of dissent, a difficult thing to achieve once the elected become powerful.