Is there a legitimate argument for design?

Sure. The Christians call it God instead of the Tao and don't call the nothingness "Wu Chi", otherwise there is a marked similarity. All we need now is for the Tao to have strong views on gay marriage ...

Well, after a few minutes with a thesaurus, how about baseless, conjectural, groundless, hypothetical, imaginary, notional, speculative, suppositional, unconfirmed, uncorroborated, unestablished, unevidenced, unfounded, unjustifiable, unproven, unsubstantiated, unsupported, unverified, or up in the air?

Now you're just being picky. Suppose I said "By definition, a vegetarian does not eat the flesh of animals". This is true; and the fact that you can't find a dictionary which specifically uses the phrase "the flesh of animals" rather than "meat" in its definition is irrelevant. And if you think it is relevant, then you should not forget that there are no rules restricting who can write a dictionary, I could turn out a very short one myself. A lot of words would be missing, but you'd find at least one entry under V.

I wonder what you mean by that? That is because its authority is not usually leant on by people saying "Such-and-such a thing cannot be definitionally true of x because when I look in the Merriam-Webster dictionary under x I don't see the exact phrase you used." However authoritative it is, it doesn't have enough authority to let you do that.