[PHI 3000] The Banana Argument for God's Existence

One of my students brought this to my attention:

It looks like a variation on the argument from design.

In that respect, my students and I discussed the fact that those who appeal to design seem to assume that one instance of design is supposed to entail that there is a designer. But what about all the things that do not appear to be designed (e.g., rocks)? Supposedly, the mark of design should be equally present in all things, since everything is supposed to be designed by God.

In other words, a proponent of this version of the argument from design could argue as follows:

1. If something exhibits design, then it must have been designed.
2. Many things in nature (such as bananas) exhibit design.
3. Therefore, many things in nature have been designed.

On the other hand, an opponent of this argument could argue as follows:

1. If something was designed, then it must exhibit design.
2. Some things (such as rocks) do not exhibit design.
3. Therefore, some things were not designed.

As Hillary Putnam once put it, one philosopher's modus ponens is another philosopher's modus tollens.

Of course, proponents of this version of the argument from design could always reply by saying that God chose to make some things such that they appear to be designed and other things such that they do not appear to be designed. Would this be a convincing reply?