[collectedparts]

Nit: I think you meant "I don't think anyone would dispute that it's a blow".

Saying "I don't think anyone would argue that X" means "I don't think anyone thinks X".

[CPLX]

I think his phrasing is also grammatical English. The degree to which it sounds right or wrong is probably idiomatic.

"it's a blow to the chest for Plaid" is a coherent phrase

"I don't think anyone would argue that" is a coherent phrase that contains a pronoun, "that." The antecedent of this pronoun is that first phrase.

I don't think anyone would argue X can mean the statement X is so true nobody would argue it.

An example would be "I don't think anyone would argue the legitimacy of George Washington as the first president of the US" or "I don't think anyone would argue the merits of food when you're hungry"

Therefore the phrase can be correctly interpreted to mean:

I don't think anyone would argue that -> [it's a blow to the the chest for Plaid]

[jonny_eh]

> is so true nobody would argue it.

You mean: is so true nobody would argue AGAINST it.

The ambiguity is whether argue means FOR or AGAINST.

[CPLX]

Indeed. Which makes the sentence work.