Of course there is incentive for Romney to use this type of coded racial language.
1. It's red meat for his base.
2. It serves to degrade Obama.
3. It helps keep white voters who might be considering voting for Obama in line by reminding them, subtly, that Obama is "other".
4. Regular white folks aren't likely to notice this type of racial insult, so there is little chance of being called out on it.
5. Minority folks who do notice, aren't likely to be paid attention to if they complain about the racial insult, because Romney has plausible deniability.
That's why it's important for regular white folks who do notice to say something and not just dismiss it as a ridiculous claim.