Earlier quoted context omitted.
When disproving a need, an anecdote is pretty effective.
Except nobody is claiming all runners need a high carb diet. If anyone actually claimed that it was that most runners would benefit from a high carb diet (I have no idea if anyone actually makes this claim scientifically).
No, one anecdote is not pretty good [scientific] evidence against anything.
I can give you an anecdote about how I drove through red lights multiple times. That does not mean you should follow the example.
Why not? You have no idea about the circumstances. I was actually talking about driving a bike, I was a teenager, and there was barely (if any) traffic. There's pro and cons there, but what matters is I omitted the details. Hence, YMMV. Plus, the statistical evidence is too small (sample size is one). Good luck reproducing the outcome, too.
Its the same in our runner's example. There's simply hardly any -if any- evidence presented to even make the anecdotal claim. Which still lacks any statistical evidence.
What anecdotal evidence can lead to is scientific research. But we should not conclude on the outcome yet. We must keep an open mind, accept on a method and test circumstances, and gain statistical relevance.
It is absolutely mind blowing, btw, how much 'scientific' research these days is not statistical relevant yet gets passed good grades (and yields the paper) at say college & universities. I'm not sure if its incompetence or laziness or lack of time or lack of money. I've even witnessed this first hand recently when my significant other was completing an assignment for her higher education degree which I was reviewing. Four interviews lead to a conclusion. Which, yes, is anecdotal ;)