Criticizing Arnold's accent is racist.
Or stupid.
Arnold's worth a half billion dollars!
What's snuffy joe worth?
Or stupid.
The question is whether he can overcome the mangling of a syllable or two -- and whether that gives him pause. But at least you attack the argument and not the delivery.
I think Arnold is right in not debating because he is the front runner. That is smart politics.
But it would not surprise me if his english proficiency is a small factor.
Also, Arnold's accent is a result of his country of origin, not his race (he would appear to be white). A xenophobe may have a problem with his accent, but a racist would object merely to his whiteness.