This would presumably be because of a poor understanding. I expect, but don't know for sure, the argumentation would be something like the following. Agriculturally produced banana trees are generally not capable of reproducing on their own. For one thing, the cultured fruit (actually a berry called a banana) is typically seedless. Such details mean that such banana sex requires humans to be available in order for it too happen.
Therefore, this surely proves beyond any doubt whatsoever that humans and bananas were created at much the same time for, should it be not the case, banana trees would never have been able to make more banana trees! Hallelujah!! And, even more proof!!! The situation is similar with cultivated maize!!!!
In reality, the ancestors of modern cultivated bananas were wild banana trees, and their sex life isn't dependent upon human intervention. And, on occassions, sexual dallies between wild banana trees and cultivated ones can result in fruit that produces some seeds. However, if you ignore those bits of reality, then some human bananas may think they've disproved evolutionary theory, not that they're likely to understand what that theory even states.