I think the problem is that you assume that there is a precise point (or even a vague continuum) where micro-evolution becomes macro-evolution. Macro-evolution may not even exist because it cannot be observed. You have simply assumed that truth of the premise by unconsciously applying the fallacy of affirming the consequent and now seek evidence to support your faulty premise.
"If you ask a scientist, they will say, there is no difference except that "macro" here means "long-term" while "micro" means "short term.""
I am shocked, shocked that a scientist would give such a meaningless answer to your question.
"But anti-evolutionists have picked up on these words, and insist that "micro-evolution" is A-OK, while "macro-evolution" is somehow forbidden."
You think maybe they simply refuse to accept the premise that you assumed was true 'a priori'? Does that make them wrong by definition?
"I'm asking, precisely where do you draw the line between them?"
That's because you assume that macro-evolution actually exists and that a line can be drawn. Since I don't believe that macro-evolution exists, I wouldn't be able to draw a line now would I? Again, does that make me automatically wrong? It's like me asking you to define exactly which biological system could not have been intelligently-designed (without committing to the fallacy of appeal to perfection, btw).
What evolutionists do is commit the fallacy of affirming the consequent. That is, they assume that macro-evolution is true because macro-evolution 'predicts' change and since you see 'micro-evolutionary change' you assume that means that macro-evolution is true.
It is a logical fallacy, however and no good foundation for what is supposed to be a 'scientific theory'.
Dan -- can I call you Dan? -- you sound like a smart guy. You have lots of facts & quotes at your finger-tips, and you handle these arguments just like you've been doing it for a long long time. You know the characters, you know the play, right?
So, if you Dan make a silly mistake, it can't be because you don't know what you're saying, or because you haven't really thought it through, can it? Indeed, if you make a silly mistake, doesn't it have to be only because there really isn't a better answer out there?
In other words, if Dan puts forward a ridiculous argument on some particular subject, it has to be because the anti-evolutionists just don't have a serious argument to make on it, right?
So let's look at what you just said. Now the great hew and cry of anti-evolutionists is: "micro-evolution" is A-OK, but "macro-evolution" is forbidden by the "scientific laws" of intelligent design creationism, right?
So exactly what is it that's forbidden? Well, Dan, you just told us: since it doesn't exist, it can't be defined. So some evolutionary process, named "macro-evolution," which can't be defined because it doesn't exist, therefore doesn't exist because it can't be defined, right?
And this is a "scientific law" of ID-Creationism, according to GourmetDan, is that about right?
And yet, if real scientists tell us that "macro-evolution" is nothing more than "micro-evoloution" over the long term, Dan will insist that is necessarily false, because, even though he can't define what "macro-evoloution," is; he is certain by the laws of ID-Creationism, it's not that, right?
Right.