This explanation isn't logically complete. It starts by asking why division by zero is undefined and concludes with "0/0 = 2, which is just not true."
But how can it be "just not true"? The point of this exercise was to investigate whether we can find a definition for division by zero, and here we've just produced a candidate! You could just define division by zero to be 2 and move on. To throw away this possibility at this point is to assume the conclusion.
It's not obviously false that 0/0 = 2 (yet).
The problem comes in when you repeat the exercise on a different example and find that also 0/0 = 3, or whatever. And now you start to see something is really amiss.
But how can it be "just not true"? The point of this exercise was to investigate whether we can find a definition for division by zero, and here we've just produced a candidate! You could just define division by zero to be 2 and move on. To throw away this possibility at this point is to assume the conclusion.
It's not obviously false that 0/0 = 2 (yet).
The problem comes in when you repeat the exercise on a different example and find that also 0/0 = 3, or whatever. And now you start to see something is really amiss.