Ainslie managed a first and third place to close the gap on Finn class leader Jonas Hogh-Christensen to three points - but there was plenty of acrimony after the Dane and Dutchman Pieter-Jan Postma managed to get the Briton handed a penalty.
"Basically he and the Dutch guy teamed up to claim I hit the mark," said Ainslie, who had to do a penalty turn as a result.
"It seriously p****d me off because I didn't, but there was not much I could do about it.
"They've made a big mistake. They've made me angry and you don't want to make me angry.
"It is sport, they're going to take any advantage they can. I don't particularly appreciate it because I'm sure I didn't hit the mark. Maybe their time will come.
"It's happened to me a lot in the Olympics before but I guess I'm older and wise enough to know not to fall for it. I took my penalty and I was determined to get past him at the finish and set myself up for the final push.
"If that is the way those guys want to play it then fine. They have fired me up for tomorrow.
"It was good to claw those points back today and there is going to be a lot of pressure for Jonas to hold on."
Hogh-Christensen was unrepentant and accused Ainslie of using disgraceful language in their resultant set-to.
"Ganging up is a hard allegation," he said. "I don't think anybody teams up to call somebody on that.
"I saw him hit the mark, I think the Dutch guy saw him hit the mark, so if two guys see it, it's probably because he hit the mark. There was no bad words from either of us, we just called him on it.
"He used words I couldn't repeat here. They began with c and f.
"We try and race by the rules and he should do his penalties. If he didn't do it why did he do his penalties?
"If he really thinks we ganged up on him then he should protest against us for bad sportsmanship."
Ainslie, 35, won gold in the Laser class at the 2000 Olympics in Sydney before triumphing in the Finn class in Athens and Beijing.
There are two races left on Friday plus the medal race on Sunday for Ainslie, 35, to claim a fourth Olympic title.
"I watched the girls winning the gold medal in the rowing and Bradley Wiggins smashing the time trial and that was a big inspiration," added Ainslie. "I thought to myself, 'If they can go out and do that, why can't I?'
"You see British people performing really well at the highest level and it inspires you to do the same."
- Sports & Recreation
- Ben Ainslie
- Olympic gold medal