The ref was biased in the sense that it was clear he was very concerned that McGregor was going to do something prohibited by boxing rules and was keeping a close eye on him, which is understandable. McGregor was stepping into a sport where the powers that be did not want him to win and they would lose face if he did, but he should have known that going in.
During the fight Floyd turned his back many times without warning or stoppage, however McGregor committed many more fouls overall and got away with a fair amount of illegal tactics.
With regard to the fight being stopped, it was a good stop. The ref could have let it go on until he was knocked down, but Conor was in big trouble and Floyd smelled blood and was dismantling him. Personally I think the ref saved him from additional brain trauma.
Conor should have actually done what he said he was going to do, namely go all out in the first 4 rounds. It was his only chance IMO.
Outside of the grandstanding during the instructions, Byrd wasn't biased against Conor at all.
RE Mayweather "turning his back," that's not what happened at all. Conor was pushing him into that position and taking his back. This is something that the boxing commentators who called the fight except for Malignaggi got wrong, but all of the MMA journalists who do fight breakdowns (including Conor fanboy Robin Black) got right in their post fight-analysis.
Conor was taking Mayweather's back deliberately and then throwing rabbit punches. He didn't get one serious warning (i.e. where the ref stops the action and lets the fighter know that he's committed an infraction), and he didn't get a point taken. Honestly, he could have be DQ'd for all the times that he threw hammerfists. Byrd actually did a great job of giving Conor the benefit of the doubt in those situations because if he'd penalized him or stopped the fight, there would have been a fucking riot and people would be complaining about getting screwed out of their money for buying the PPV (which is ironically actually what happened anyway).
Additionally, there was absolutely nothing wrong with Mayweather's reaction when he was pushed into those positions. Boxers are not trained to fight or defend with their backs turned, so he simply defended the back of his head and waited for the break.
Finally, Conor complaining about the stoppage is laughable. He was literally staggering around for over a minute getting while hit with clean shots and not even attempting to throw back. Not only is that a good stoppage by boxing standards, it would also constitute a good stoppage in MMA. That's exactly how Rousey/Nunes got stopped and, outside of Michael Rappaport, I don't remember anybody complaining about it.
...and what the fuck does the fact that Robert Byrd is married to Adelaide Byrd have to do with anything? I'd say that it's surprising that Conor has so many fans who blindly accept all of his ridiculous and patently false statements, but then I have to remember that the incumbent POTUS has the same kind of following.