Making myself look stupid? Please take a moment to consider.
This is his original line: "Couldn't of said it better."
This is what it should have been: "Couldn't have said it better."
The lexical item 'of' is NOT a verb, it's a preposition, it's being misused. The auxiliary verb 'have' is required before the verb 'said' in order for it to make sense, it's past tense.
You might be a little confused, you say "You literally said of was the verb"... where did I?
It's a really common grammatical error - as I said before, because the phonetics are very similar between 'of' and 'have', or abbreviated 've.
If you still can't see where you're both wrong, it's a lost cause.
Never found a better use for the "Thanks" button. Well maybe I have but wuteva.