Oh please. The same rhetoric is used by liberals when a state whose majority demographic is poor, uneducated whites (who would very much benefit from government programs) vote for republican candidates who would stifle government funding for programs under their policy. It's not necessarily used against minorities/oppressed groups exclusively, its a phrase meant to describe anyone who might not recognize the potential economic benefit they could receive under a candidate's planned policy.
The intent of the phrase is not to come off as racist. I do think the rhetoric of "that candidate is what's best for you" is problematic in that it indicates a sort of "I know better and you should listen to me, please" without providing much substance for the argument as to
why that candidate is best much of the time. In cases where that substance
is provided, I think the "what's best for you" bit is obviously a little more valid and justified. Using it willy nilly is going to build ire amongst the people you're disparaging, as seen by the portion of black liberals who are hesitant to support Bernie because his supporters seem so hesitant to view blacks who don't vote for Bernie/vote for Hillary over him as a group of intelligent individuals. But let's not pretend that that phrase is intended to specifically make blacks feel bad. It's intended to make anyone who doesn't agree with Berns feel bad. I don't think it's a good strategy, but it's certainly
not a racist strategy, not as far as I've seen, anyway. It beats up all demographics equally assuming they don't agree with Bernie supporters.

You might think that it occurs to blacks more than other groups (and that its code to refer to blacks in a racist manner) because that's your lived experience, and that's certainly valid, but my own personal experience tells me my liberal friends use it against my white self to disparage me for my Bernie skepticism. The phrase seems to be demographic-blind.