Fairclough revealed he was hurt by the abuse he suffered from a minority of supporters during last weekend's 4-0 home humiliation by Notts County .
But his plight was not helped on this occasion as goals from Martin Gritton, Francis Green and Nat Brown condemned the Bees to another miserable defeat.
Fairclough, who has been in charge for four years, has come under fire from a number of supporters following the club's disastrous start to the season.
And despite an improved second-half display which saw John O'Flynn head Barnet level, the Bees were unable to avoid a third loss in seven days.
After conceding seven goals in their past two games, you could excuse some of the home players looking short of confidence but Barnet started brightly with the lively Albert Adomah buzzing around as usual.
And it was the home side which threatened to take the lead as O'Flynn turned beautifully inside the penalty area before lashing an effort against the crossbar from 10 yards.
It was a huge let-off for Macclesfield, who had been off the pace in the opening few minutes, but they hit back in style thanks to a delightful finish from Gritton.
The former Torquay striker, who had just wasted a golden opportunity after being played through in goal by Simon Yeo, produced a moment of magic to break the deadlock.
Barnet failed to clear Yeo's cross and Gritton sent an acrobatic left-foot volley into the top corner from 12-yards with Lee Harrison a helpless spectator.
Macclesfield should have extended their lead with Yeo's flashing drive landing just inches wide of the far post, while Gareth Evans produced a contender for miss of the season after failing to slot home from two yards.
And they should have been severely punished for that miss just minutes after the break as Neal Bishop's pinpoint cross picked out O'Flynn just six yards from goal, but the former Cork City man could only head straight at Jon Brain.
But O'Flynn made amends soon after, bravely heading home at the near post after Luke Medley's cross had caused panic inside the Macclesfield backline.
The home side continued to bombard the Macclesfield backline with Medley heading inches wide from Adomah's cross, while the same player burst clear before firing just beyond the far post.
With Macclesfield hanging on, Jonny Brain was called into action once again, this time rushing out to deny Bishop as the Bees skipper threatened to run through on goal.
Brain was at it again just minutes later as Adomah took aim just eight yards out, but the Town keeper produced a stunning save to keep his team level.
And that save was to prove crucial as just moments later Macclesfield snatched the lead as Green lashed the ball home from 20-yards to leave Underhill in stunned silence.
That goal knocked the stuffing out of the home side and Brown's late header was the final humiliation as Barnet's winless streak was extended to eight games.