But we can all agree that a hamburger with actual shit in it is worse than a hamburger from Smashburger, just as there are certain actions that are clearly morally wrong and don't need to be evaluated with some false fairness.
I'm sure that out of the 7 billion people living on our planet, at least one person genuinely likes the taste of shit. To them, this wouldn't necessarily be true (I've never had a Smashburger and I don't like the taste of shit, so I couldn't possibly make this comparison myself). Which is why it's not objectively worse. It's all based on the person eating the burger, because everyone has different likes and tastes. That's why there's never one burger option; everyone shockingly doesn't like the same things.
No, you should have used an analogy that actually works.
Preferences for death or risk of death are not exactly unknown, so, while that may be true, it isn't sufficient to establish the universal preference you've offered it to support.
> Should I have said cyanide instead to get the point across?
No, for the same reason. The problem isn't the example, the problem is that the point is wrong; whether or not one believes that an absolute morality exists (in whatever sense of "exists" makes sense for morality), you aren't going to any of its contents through universally-extent preferences, just as you won't for food, because preferences aren't universals.
There's nothing that objectively makes a hamburger better than another. It's all subjective, just as views are subjective. Some people like bread a lot, so they may want a really thick bun which could be overpowering to another person. Some people are vegetarian, while others cringe in disgust at a black bean burger. It doesn't make those hamburgers any better or worse than others, though.