Holleh Nowrouz was dismissed by Sharks chief executive Steve Diamond following a "stringent disciplinary review" after her comments, which were posted in October, came to light last week.
Nowrouz wrote: "Oh, the joys of managing a sport club's social media when we've lost the last 7 Premiership home games. To the Sale Sharks fans who comment about the club needing to spend less time blogging and tweeting and more time coaching, the staff who create content for the website and social media platforms are not the same members of staff who coach the team. You absolute f***wits."
Sale issued a statement last Friday which said that internal disciplinary action had been taken and that Nowrouz "deeply regrets" her comments.
On Monday, Diamond announced the 26-year-old had been sacked.
"As a club, we have always been proud of the backing we receive from our supporters through thick and thin over our 151-year history," Diamond said.
"At this crucial time for the club Holleh's comments, though private, just overstepped the mark and left her position untenable."
Sale were beaten 25-18 by Wasps on Sunday and are bottom of the Aviva Premiership with just one victory from 11 matches, and five points adrift of London Irish.
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