It should be reopened
To be clear: this is not a good question. But that is not, and hasn’t ever been, reason to close something. Close votes are not super-downvotes.
The motivations expressed for closing aren’t really right:
I’ve voted to close as unclear. Dathomir isn’t a race, it’s a species.
If we can close for this, we could close for someone asking whether Palpatine was “racist against clones” (they’re not a race, they’re all the same person). We could close a question for asking whether Tolkien was "racist against the East" (the East isn’t a race, it’s a region containing a collection of cultures and societies). Both these questions, phrased a little differently, have been well-received on this site.
It’s very clear what they’re asking. Yes, “speciest” is the right term (if one believes that the different Star Wars humanoids qualify as different species), but many people use “racist” anyway. It’s a well-established usage in this context, and is easily inferred otherwise.
A simple edit would have corrected this. Now that this edit has been made, this motivation for keeping it closed doesn’t make much sense.
And let’s be clear, the question isn’t unclear in any other way. Its meaning is stated precisely at the end of the question:
Does Obi-Wan have specially motivated hate towards Dathomirians and/or
other non-human species (potentially due to his traumatic encounter
with Darth Maul and the sheer amount of other confrontations)?
It’s not opinion-based. Is Was the Emperor himself xenophobic? Or was that merely a political point? opinion-based? What about Was Hagrid guilty of blood prejudice? (which some people might find equally implausible)? If we need really clear evidence before a question can be asked, what about Was Snape romantically attracted to Mulciber?.
The case for it being opinion-based is also undermined by some of the comments about closing it:
You might wish to note that the Tuskens (in the canon Star Wars: From
a Certain Point of View) refer to themselves as Sand People on
This is canon evidence against the idea that Obi-Wan was prejudiced: in other words, a negative answer. This question is answerable. Many of the close voters seem to think that it’s clear that Obi-Wan was not prejudiced—clear evidence that the question is not opinion-based. In any case, “We don’t know, but there’s not any real evidence of it” is a perfectly acceptable answer.
All the other motivations for closing seem to run afoul of one or more well-established policies:
Close votes are not super-downvotes. This is a long, long-established policy:
Don’t close a question just because you don’t like it, or it sucks.
Close for one of the valid reasons. Closing is not done enough, but
should not be undertaken lightly. Look over the reasons – if you feel
the question qualifies, do it. Others may or may not follow.
Not knowing whether there’s an answer to a question is not a reason to close it. It’s impossible to know whether there’s an answer out there, even if one can’t think of one:
I agree with PearsonArtPhoto, questions should not be closed on the
grounds that they don’t have a canon answer, and I want to specially
emphasize one particular point: the only way to know a question is
unanswerable given canon is to know all canon in a universe, an
unreasonable bar to set for most topics asked about here. Even I have
seen questions here that I thought had no canon answer, which
eventually did receive one.
In a universe with a very large amount of canon (LotR, Star Wars, Star
Trek, etc.) how is an asker to know whether a particular piece of
information is in canon? We don’t require users to have read canon
before asking about it, so how could an OP know that it wasn’t
answered in canon?
We don’t close questions for using the wrong term. We just make an edit and inform the poster. Or, perhaps, we don’t even make the edit at all.
We don’t close questions with incorrect assumptions. We correct the assumptions in an answer or in a comment.
We get bad questions all the time, and they’re quicky relegated to the bottom of the heap. That’s what downvotes are for. It’s the SE philosophy. Close votes have never been for penalizing questions for containing incorrect information or starting with preconceptions, and I don’t see any reason to start now.