Why is there a problem with CGI?  I see the rule, but the reason for it is obscure to me. Not trying to rock the boat, just would like to understand why it is anything to get upset about.

In and of itself, CGI isn't really a problem. However, in almost all cases (including this one), the CGI is the main focus of the save it's in. There are some exceptions, like text plotting (as long as the text is actually serving a purpose), but in general, CGI just doesn't really add anything of value, to TPT.