There is nothing flawed about disagreeing with experts. What matters is whether you have enough evidence to support your conclusion. Whether that conclusion goes against experts’ views has no bearing on the quality of the argument.

By using “if Professor V is correct,” the conclusion is conditioned on the hypothetical situation in which Professor V is correct. This does not assume that the professor is in fact correct. So the author doesn’t assume that Professor V’s claims are true.

The premise asserts that if Professor V is correct, there’s not enough evidence to say that glassblowing began in Egypt. We accept this premise as true. It doesn’t matter whether we know the criteria for adequate evidence.

The author labels the view of “most historians” as the “traditional view.” We have no reason to think this labeling is wrong. In any case, whether a view is traditional has no impact on the argument. The author never rejected a view because it was traditional or not traditional.

The author confuses inadequate evidence for the truth of a claim (that glassblowing began in Egypt) as evidence that the claim is false. This is a flaw because a claim can still be true, even if there’s not enough evidence to prove that it’s true.