Using his personal website, Farina wrote a spirited message to respond to the 'uninformed' fans who have started a Twitter campaign using the hashtag #FarinaOut hoping to get the Sydney boss sacked.
Farina questioned whether his critics are actually "real football fans" and urged everyone to unite behind the team.
The Sky Blues, who missed the finals last season, have struggled over the first month of the season and have lost their last three games without scoring a goal.
"I do have a question for those people - who mostly hide behind fake names or no name - who hurl mistruths, abuse and personal insults at me, some of the staff and the players. Are you really real football fans?," Farina wrote.
"The campaign for #FarinaOut, the uninformed and inaccurate speculation about injuries, the constant hectoring about drinking - you need to know that they're water off a duck's back.
"A real football fan follows their team through thick and thin. A real football fan, when faced with one win and three losses for the start of the season, is asking what they can do to help get the team on track.
"A real football fan doesn't write an expletive laden message about not going to the game on the weekend, but realises this is the time more than ever that they're needed at home against their biggest traditional rival.
"I know this because I've done nothing else except work in football since I was 17. I've seen and met real football fans in Australia and all over the world."
Injury to skipper Alessandro Del Piero has contributed to Sydney's slow start to the campaign but the Italian veteran looks certain to start Saturday night's crucial clash with Melbourne Victory.
And Farina says this week's clash at Allianz Stadium is the perfect opportunity for Sky Blues fans to show they are behind the club and help turn their season around.
"A real football fan has their team's back," Farina continued.
"That's what makes a great club and, in the Australian context, that's what will be the next  big step in the development of the game in our country.
"I can promise you that there's not one player and not one member of the coaching staff who isn't striving week-in, week-out.
"Sydney till you die? Terrific. Prove it."