Because they are part of the democrat plantation, they have sold out their fellows for their own perceived gained. That to me is an uncle tom. Some may be sincere, but at this point, given how the left exploits them and keeps them ignorant and in poverty, for them to continue towing the rat line, while at the same time hating on those who are conservatives is, to me, the definition of selling out.
And yes, I am referring to liberal commentators, many of which work at espn.
Oh, I understand your perception of the term, but it's not commonly understood to have that meaning.
Among blacks, an 'Uncle Tom' is a black person who isn't 'down for the struggle' against the majority culture/population/traditions, or you're someone who considers themselves to be part of the mainstream.
In other words, if you're not a honky hating, class warfare raging, black power advocating Marxist, then you're a 'sell out' to the 'cause'. You're a disgraceful, self-loathing black person, who doesn't deserve the skin you were born in.
That'd be me.