Saadia Gaon's "textual" proof - crumbles like apple pudding

A few years ago I had a discussion with R' Moshe ben Chaim about textual proofs for the Oral Law. He made the following statement:


"Someone on your blog wrote that I said there is no textual proof for Oral Law. However, I don't believe saying that for one reason: Ibn Ezra quotes the "Gaon" ("genius", referring most probably to Saadia Gaon) (Exod. 24:12):
"The Mitzvah: [this refers to] the Oral Law, for all the commands were given to Moses at Sinai, during the days he stood on the mountain."
Ibn Ezra is of the opinion, as are all Talmudic and Mishnaic Rabbis, that both, the Written and Oral laws were given to Moses ta Sinai. This historical truth was never disputed by the original Torah recipients, throughout the Mishnaic and Talmudic periods. Therefore, it is impossible for someone subsequent to the original recipients of Torah to suggest an alternate history.
I strongly request you post this for others to read.
Regards,
Rabbi Moshe Ben-Chaim"

My response was as follows -

I would like to explain why it is important that we work with the Rabbis who are bold enough to accept our challenge, in discussing these very controversial issues.
Firstly, no individual should be arrogant enough to think that he is wiser than everyone else.
Secondly, even if one fervently is convinced of his position, he should be open minded to hear the other point of view.
3rd, most orthodox are loathe to enter such a debate, they consider it long dead and buried, since the karaites no longer hold much of threat to them.
4th, we get invaluable sources too.
Now, let me comment on the textual proof attributed Saadia by Ibn Ezra.
The verse is Exodus 24: 12
And the L-rd said unto Moses "Come up to me into the mount; and be there: and I will give thee the tables of stone, and the Law [Torah] and the Mitzvah, which I have Written, that thou mayest teach them. "

Now, the Ibn Ezra/ Gaon claim that the two words Torah and Mitzva refer to Written and Oral laws respectively. Hence, this is a textual proof against the Karaim. However, if we actually look at the verse, these two words are followed by "which I have Written" or Asher katavti.

So the Law and Mitzva here are Laws and commandments which have Been Written. That is the meaning of the Text. So this very verse which the Gaon is claiming as proof for oral law only proves that G-d was commanding Moses about a Written law. In fact, the words Asher Katavti are a very powerful Disproof of any imagined Oral Law.  Any fool can take half a verse and leave out the words which go against his own ends. That is not scholarship, but deception.

As in the case of the Sefer Torah of the King, the absence of any requirement of oral Law repudiates the claim that Torah needs an oral law in order to be fully functional.

So, I am afraid that even Gaonim, who lived 1000 years ago were so blinded by their own ideology as not to see the plain meaning of a verse, and its implications. And, that myopia has been preserved religiously for so many generations.