interesting point, are you suggesting refs are doing this consciously or unconsciously? If consciously is your answer I will suggest you are deluded.
Certainly the large majority of gripes people have with ref's giving the all blacks preferential treatment is coming from confirmation bias; simply, people see patterns when they aren't there, people notice the evidence that supports their point and not the evidence against it.
But I'm not dismissing some not insignificant unconscious bias toward the ABs on behalf of the ref's, perhaps simply because they unconsciously interpret wrong-doings from lesser teams as them resorting to cheating out of desperation. I'd be interested in your thoughts of how this bias comes about.
Maybe, but you have less evidence for this than the people claiming the refs favoured the All Blacks. It's pretty easy to point to a series of decisions and wonder what the **** is going on, much harder to gauge the mental state of the people making the judgment on the refeering performance beforehand. Unless, of course, you just assume all viewers are bias against the All Blacks, but that would be ridiculous.
No, it is far more likely that, if after a game the consensus is that the referee favoured the All Blacks, that he actually did and we don't all suffer mass delusion. Although mass delusion probably makes you feel more comfortable as an All Blacks fan.
Refs favouring the dominant team happens all the time in rugby, and not just where the All Blacks are involved. It's common knowledge that if you win the early scrums the ref will be far more likely to side with you for the rest of the match. This is because so much of rugby is based on subjectivity. This is also part of the reason why people prefer simpler games with less room for interpretation such as league or soccer.
Of course, you cover your bases by stating that even if there is some unconcious bias towards the dominant team, which there usually is, its insignificant. Even if only one decision (such as the 30 meter advantage) goes your way and arises out of unconcious bias, then it's already significant. Particularly in test match rugby where the margins are often very slim.
I'll grant you though, that the only reason the All Blacks in particular get hit with the accusation of refereeing bias is because they are so often dominant, and refs tend to favour the dominant side. Makes sense really.