The conclusion is that EE Cummings stood against something essential to his own work. Why?

First, EE Cummings stood for the individual human against regimentation and standardization.

Second, metaphor requires literal language, which in turn requires regimentation.

We’re trying to prove that EE Cummings stood against something essential in his own work. The only thing we know EE Cummings stood for is being against regimentation and standardization. So something in EE Cummings’ work must involve or otherwise support regimentation or standardization.

We have premises that establish metaphor involves regimentation. But what does this have to do with EE Cummings? We don’t know. The author never explicitly stated that metaphor was essential to EE Cummings’ work. But if we can learn that it was essential to his work, that would establish that there’s a conflict between what EE Cummings stood for (being against regimentation) and something essential in his work (metaphor, which involves regimentation).