In short, race is irrelevant to the criteria I use to judge moral relevance, and that is why I am not a racist. This is also the same reason I'm not a speciesist: the species isn't relevant. I may judge a bacterium to not be morally relevant, but it's not because of species. It's because the bacterium lacks the traits I believe are are salient to moral relevance.

You believe, presumably arbitrarily, that sentience is the only criteria with which to judge moral relevance. So you are presumably not a racist because of your arbitrary belief that race is not morally relevant. You didn't really explain why you have your belief, so I am only assuming that you hold it arbitrarily. In any case, that was not within the restrictions I imposed.

I'm suggesting it needs to be more than a simple description of an attitude toward something. Imagine we're roommates and I like chocolate more than vanilla. You like vanilla more than chocolate. I throw away all the vanilla to make room for the chocolate. That I prefer chocolate wouldn't be a justification for that act, but it could be the reason I threw away the vanilla.

Okay, that's not what the word 'justification' means. So you've been artificially restricting what can be defined as an ethical proposition. In the example you just gave, you're just defining a special meaning of justification which is wrong.

So it didn't demonstrate anything to me and I can't respond to it at all unless you clarify it.

I stated it explicitly in the antecedent post in the thread you read to reply initially to my post, so I assumed you had read my post, my bad.

I didn't argue against that. If there was an argument for veganism (or against racism) that wasn't meta-ethical it would have to be compelling in every moral system, right?

Yes, the point being that the moral system is irrelevant. So for example, a lot of people object to being vegan because they think they couldn't get sufficient nutrition from a vegan diet - this is incorrect regardless of their meta-ethics.

If you read the comment chain being discussed, the person I replied to was claiming that non-vegans use irrational (i.e. invalid) justifications for their actions. I meant to show that there are simple rational justifications for veganism. This is significant for democratic societies because political decisions are made from a position of epistemic abstinence, i.e. whether vegan or non-vegan positions are framed by the 'correct' meta-ethics isn't relevant. It's not as simple as saying non-vegans use internally inconsistent justification for their actions.