Of course I can't prove he meant his comment in a racist way. That's how plausible deniability works. This is not a court, and you are not the jury, judging whether my testimony is true or false. I'm merely giving my opinion...which is what these message boards are for.
I'll give some more opinions...
Do I think Romney is a racist? No.
Do I think he's been playing race-politics? Oh yes.