Just sayin’ = justinbiebersayin’ = biebs
A common phrase in Americockney. A statement of fact.
Derived from the ubiquitous and incessant presence of Justin Bieber, a constant annoyance in modern American culture. Provides a vent for buildup of hatred, in addition to being a delightful self-referential meta-pun.
As a statement of fact: “I can’t believe you said that!! Biebs.”
To cushion the blow: “You are such a dick. Biebs.”
Basically it can go anywhere you’d say, “I’m just sayin'”