The Leicester City keeper has leapt to the defence of the Spanish stopper, suggesting that the criticizm has been disproportionate.
Schmeichel - whose dad, Peter, spent years as United's first-choice goalkeeper - told the BBC: "Goalkeepers are going to get scrutinized.
"For me, the important thing is context. The kind of scrutiny that he's getting at the moment is very harsh."
Schmeichel claimed that because very few ex-keepers become pundits, De Gea "is being judged by people who have never played the position".
He continued: "There are no goalkeepers analysing on TV or in papers so I feel the criticizm he gets is very unfair.
"They'll go into deep technical things which, with the greatest respect, they don't actually know the truth.
"To just hammer someone the way he sometimes does get hammered, I find is unfair."
Former United captain Roy Keane recently criticized de Gea following a high-profile error against Tottenham Hotspur.
Keane voiced his concerns after the keeper conceded a soft goal in the first round of games after the Premier League restart.
He said: "I'm shocked. I'm shocked at that goal.
"I've watched a lot of football over the years and to give away that goal ... I'm fuming. I can't believe that's Manchester United."
Keane added: "I would be fining him [De Gea] at half-time, there is no getting away from that.
"I would be swinging punches at that guy. That is a standard save for an established international goalkeeper."