It's interesting to note fox news has more diversity of opinion than does NPR. On NPR all minorities are progressives, yet IRL I know minorities with all points of view, but listening to them you'd think they were all progressives. So, yes, they forward their narrative very adroitly.
This morning they had a piece about WalMart increasing base wages more than originally announced, and the presenter, as an aside mentioned, "I'm sure out of the goodness of their hearts". See how insidious it is? There was no reason for that, it didn't follow from what the reporter was saying. And it's this kind of technique they've mastered.
It's not a misrepresentation to say that, e.g., blacks tend to vote Democratic. That's factual information, and it's not the same as claiming that all minorities are progressive. No one claims this. I don't even know what "narrative" NPR would be forwarding if they claimed this.
This frankly sounds a lot more like a Fox News tactic than NPR. "All minorities vote progressive!" sounds like a rallying cry to get conservatives riled up and active.
NPR does not make that untrue claim. What happens is they predominantly interview progressives when they interview majorities or minorities. In addition most of the staff and volunteers do not lean conservative or libertarian by any measure. As I said, I wager I'd see more political diversity at fox, and that's staggering, knowing about fox.
As for interviewing only progressive minority members, I'm not sure that's true. I feel like you're pushing this as a fact with no data to back it up. I mean, if they're interviewing someone from the black lives matter movement, it's probably going to be a progressive black person. But I also recall them interviewing Latinos in Florida opposed to lifting the Cuban embargoes.
I'm an independent and their con guests are somewhat lacking in style and argument.
It might be a side effect of her location (DC) and clout, but she often has influential policy makers on her show, from both sides of the fence.