Go back and read my last few posts, and you'll see that I've allowed for the possibility that one could conclude the existence of an inept or insane (or evil) designer(s) based upon purely naturalistic evidence.
OK, but I was pointing out the problem with your argument against teleology. Your proposed trichotomy (either no designer or inept designer or insane designer) is also fallacious, but before we get to that perhaps you should come to terms with your own apparent belief in teleolgy. Perhaps teleology might not necessarily be obvious in nature... but then why do you believe in it? Why do you believe that infant cancer is the result of something gone "horribly wrong"?
Again, I am not trying to prove to you that nature is teleological, but if you wish to discuss the matter logically then you need to understand why your attemped proof of the contrary is self-defeating. Is infant cancer an example of something not working the way that it should, or isn't it? If infant cancer is an example of something not working the way that it should (as you presume) then this implies that nature (at least so far as human life is concerned) is teleological, which is the opposite of what you claimed it showed. If, on the other hand, infant cancer is NOT an example of something not working the way that it should, then you have no argument to begin with.
Now, regarding the false trichotomy you proposed regarding the possibilities of a designer (or lack thereof): What do you mean by "evil", and by what "purely naturalistic" standard would you accuse the designer of nature of being "insane"? Or perhaps you have some standard in mind that is not "purely naturalistic"? Do you see the problem here?
No, the logical trichotomy is not nearly as loaded: Either 1) There is no designer; 2) There is an inept designer; or 3) There is a perfectly skilled designer.