Beith boss Chris Strain admitted his second-half dismissal took some of the shine off a triumphant return to Buffs Park.
The Mighty shot to the top of the West of Scotland League Premier Division after coming from behind to win yesterday's all-action North Ayrshire derby.
A Josh Fowler brace and Kevin Nicoll own goal saw off a battling Buffs side who started and completed the scoring through top marksman Dylan Mackin.
Both sides finished with 10-men after respective team captains Nicoll and Paul Frize saw red in the game's closing stages.
But former Kilwinning boss Strain was first to receive his marching orders after straying on to the pitch during a frank exchange of views with Buffs' striker Thomas Collins.
The 67th minute flashpoint saw Strain jeered by a gleeful home support as he walked off the touchline. And despite ultimately getting the last laugh, Strain admitted his sending off blotted a big win.
He told Ayrshire Football News: "Thomas was having a bit of verbals with one of my players, I've defended my player and end up getting sent off for it.
"Thomas is having a go, I'm having a go at Thomas.
"Why does the manager get sent off? It's a bit of double standards in that scenario but the referee says I've strayed onto the pitch."
Strain, however, was delighted to see his players get the job done despite not being at their best.
He added: "Kilwinning are a good team. They're fighting for their lives and made it very difficult for us.
"We didn't start the game well but we grew into it.
"At the points where we scored the goals I thought we were the better team.
"We didn't play as well as we can but we got the result and that's the most important thing."
Chris Millar took charge as Kilwinning caretaker boss for the final time following Chris Aitken's appointment as successor to David Gormley on Friday afternoon.
Aitken took the opportunity to watch the match from the stands and, if first impressions count, he would have been hugely encouraged by a lively start.
With just five minutes gone Buffs took the lead from the penalty spot, Mackin making no mistake from 12 yards after Conner McGlinchey fouled Gavin Miller in the area.
Blair MacIntyre skied a glorious chance to make it 2-0 on the half hour mark and seven minutes later Beith were level when Nicol turned a cross into his own net under pressure from Fowler.
The visitors got their noses in front in 57 minutes when Fowler rounded off a sweeping move with a terrific angled finish inside the box.
Strain was dismissed from the dugout shortly afterwards and referee Ross Birrell was soon flashing red again, this time at Nicoll for what was deemed a rash challenge on Fowler.
Beith looked to have wrapped up the points in the final minute of the regulation 90 when Fowler slotted home his second goal of the afternoon.
But an excellent Mackin finish and a second yellow for Frize in the two minutes that followed made them sweat until the final whistle.
Defeat leaves Kilwinning third bottom of the table and three points adrift of safety.
Caretaker Millar said: "I think the game sums up how our season has went a wee bit in terms of the goals we lose.
"We've lacked being aggressive in certain situations and I think that's what's cost us.
"But one of the things I think has been brilliant the past couple of games is the character, the attitude and the application the boys have shown.
"I think that's all that the new manager is going to want to see.
"We just need to keep sticking together. I've got no doubt we'll turn it around and get out this situation."
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