Demeaning behaviour and unreasonable attitude?
In itself, no. Because those are not objective traits. But if the community thinks so, perhaps.
I'm reluctant to say why staff might demote a bureaucrat, as it's rather complicated on all and likely taken on a case-by-case basis . . . I'd say that things such as death threats, constant copyright violations, and impersonating staff members would result in very likely demotions.
There's other reasons, for sure, but I would say that if you have a specific issue with a bureaucrat then there's a line of action to go through, which I - or someone else - could send you . . . this starts with trying to resolve with said bureaucrat, with talking to staff as a last resort (or a first resort in case of death threats or severe abuse/harassment).
You can also ask in the forums with specific types of behaviour, perhaps examples, so that way people could give you more specific advice, too.
I had trouble talking to Hey1234, admin of Disney Wikia. He rebuked me for my statements. He thinks they are nonsense.
He won't likely get demoted for that.
To be honest, I agreed with some of what was said (at a glance). It just seemed that the two of you argued over semantics and he blocked you for a very short time, and now you're allowed back on the wiki, with all having been resolved. If we keep this strictly on-topic; staff are very unlikely to intervene based off personal disagreements, and he doesn't seem to have broken any ToU (that I know of as a regular user and not a staff member).
I'd personally advise to let it drop, as it might cause more drama by going over and over the issue and aggravate the bureaucrat in question, but - if you can't - you can always politely discuss it with him, providing you stop if/when he asks you to stop. Often, these things can also be resolved with polite discussion and each side listening to the others' points.