It's not quite as simply as whether it's Turing complete or not. Just because a language is Turing complete doesn't mean it has access to the libraries/hardware. The point I was really making about BASIC is that it has access to all of the SWIs, which makes it as flexible as any other language in terms of the resources and parts of the OS it can access.
Although you *can* use bad programming practices in BASIC, the same is true for C, C++ or many other languages. In my opinion (and as SimonC says) there's enough structural stuff in BASIC to learn good practice.