The barbarous and hellish power is the British empire, the full context of the quote is far more anti-British than anti-"Indians and negros". It's basically saying "the empire is stoking ethnic divisions in the colonies to maintain dominance over them" but the wording is, perhaps, a bit problematic. Also, Hexbear is always going to be more sympathetic to the pro-British black and indigenous communities than Paine had been, for obvious reasons.

In addition to what ham said, Paine was writing to a settler-colonist audience who greatly resented occupants of the land who weren't white, so it's an easy appeal to the audience to stoke racial animosity and "blame it on the guy who is responsible for all the other problems too"