Hull City man Boyd clashed with Manchester City goalkeeper Joe Hart in the second half of his side's 2-0 defeat at the KC Stadium last weekend, with Hart appearing to accuse him of diving in an attempt to win a penalty.
Hart was booked by referee Lee Mason following the incident and escaped any further punishment, but Boyd was charged with spitting at the England international.
The 28-year-old denied the charge but his appeal was in vain, and he has since been handed a three-match ban by the FA.
Hull manager Bruce has revealed Boyd was "horrified" by the accusation and was prepared to go to any lengths to clear his name, while also insisting the club should have been able to provide a defence at the subsequent FA hearing.
"We did all we could but as soon as they've charged him, I think we all understand that they're not going to change it and I don't know why this so-called committee sits," Bruce said on Friday.
"For me we don't get a fair hearing of it.
"The system needs to be looked at. It's like a kangaroo court. We don't know who's on it, who makes the decisions, who is accountable for it.
"For George himself, he feels that strongly about it, that if there was legal action to take, he would take it. It's accusing him of something that's not in his make-up at all. I'm 100 per cent behind him.
"I can see on the television and you can see that there's a bit of saliva came out of his mouth, that's not deliberately spitting at someone, he's shouting at him and it's come out of his mouth.
"I know certain players where you would say 'OK, he's capable of it', certainly not George Boyd.
"Joe Hart last Saturday comes out and says that he didn't deliberately spit at him. You know if somebody spits at you and he's only a foot away."
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