Many supporters called for Sinnott's head following Vale's dismal display in the first ever league meeting between these two sides.
Sinnott sprang a surprise before kick-off by dropping goalkeeper Joe Anyon and bringing in 18-year-old rookie Chris Martin for his league debut.
But it was Martin's opposite number, former Vale keeper Jonny Brain who was in the thick of the action in the early stages.
Brain saved well from Simon Richman, Marc Richards and Luke Rodgers inside the opening 12 minutes as Vale made an impressive start.
Macclesfield survived the storm to hit back as the first half wore on and Luke Prosser did well to cut out a dangerous cross from James Jennings.
And the visitors stunned the home crowd by taking a 36th-minute lead after Luke Prosser's foul on Jennings 20 yards out.
Terry Dunfield curled the resulting free-kick past the defensive wall and just inside Martin's left-hand post.
Vale equalised from a free-kick in a similar position a minute before the interval after Richards had been sandwiched by two defenders.
Richards' shot came back off Brain's right-hand post to Louis Dodds, whose follow-up effort was going in when Macclesfield defender Shaun Brisley belted the ball into the roof of the net.
Macclesfield's confidence was undiminished, however, and they should have gone back in front when Danny Thomas dallied with the goal at his mercy eight minutes after the break.
And they did regain the advantage when the referee incensed the home fans when he awarded a penalty for Lee Collins' challenge on Izak Reid 15 minutes from time.
The decision was debatable to say the least, but Simon Yeo didn't ask questions as he fired in his spot-kick off the underside of the crossbar.
Yeo sealed victory for the Silkmen seven minutes from time when he pounced on a dreadful mistake by Chris Slater to fire home his second.
And the Vale fans were already flooding out of the ground when Reid turned to hook in a spectacular 20-yard shot two minutes later.