"Margarine is one functional group away from plastic"

No its not that, and it is easy to debunk this myth, the longest chain of hidrocarbons a fatty acid in margarine could have is 22, that would be the equivalent to docosane in terms of alkane, wich is not a plastic obviously, it is powder like substance that didn't posses the polymers chain necessary to perform plasticity, in polyethylene reaching thousands of groups repercursively repetited.

The suspicious part in margarine cames from the fact that it is durrable against hydrolisis degradation, that would form butyrate, that attracts animals and insects on the natural decomposition of butter.