Multiple sources tell The Daily Beast that the conversation earlier this year became acrimonious, with Halperin dishing up vague threats against his former boss.

MSNBC declined to comment on the episode. But MSNBC insiders said Griffin was furious about the conversation and wouldn’t likely take Halperin’s calls in the future.

The hostile exchange was a sign of Halperin’s frustration that his dream of returning to the punditry business—almost two years after numerous women came forward with stories of sexual misconduct—has been thwarted at each turn.