The 20-year-old has attracted negative headlines after he was pictured inhaling laughing gas as well as holding a shisha pipe.
"He's one of the most talented English players coming out of this country - Do not destroy him," Campbell told The Guardian.
"Wayne Rooney did a lot of stuff, he got some flack, but it was almost overlooked: 'Oh, you've been a bad boy, let's overlook it again.'
"Raheem Sterling is one of the most talented men coming out of this country. Wake up. PFA, wake up, press wake up and protect this boy."
He added: "Do. Not. Destroy. That. Man. Yes, he's young, yes, things will happen, and [Liverpool should] pay him the money because he's worth it."