Manning enjoyed one of the greatest individual seasons in NFL history this term as he broke the records for touchdowns and passing yards in a single campaign, but he received criticism for his under-par performance in the Broncos' 43-8 Super Bowl defeat to the Seahawks on Sunday.
Sherman leapt to Manning's defence on Twitter after the match, before explaining why he had felt it necessary to publicly back the 37-year-old.
"People shouldn't have to write to bash him after the season he had and everything he did, everything he's accomplished in his career and this year as a football player," Sherman told ESPN.
"He is a Hall of Fame player, he's a living legend, he's a record-holding quarterback, he's a Super Bowl champion, he's been a Super Bowl MVP.
"I think if you want to criticize his play on the field, that's fine. But don't call some of the things that they were calling him."