Sen. Bernie Sanders, I-Vt., joined Stephen Colbert on "The Late Show" Thursday night where the host couldn't resist asking him to comment on recently released excerpts from Hillary Clinton's book that reflect on their primary battle.

Though Clinton's words for the senator were so harsh they turned heads this week, Sanders did not reciprocate, choosing instead to stay positive and argue it's time to move forward from 2016. He did, however, level one choice dig at his former opponent.

"Look," Sanders told Colbert, "Secretary Clinton ran against the most unpopular candidate in the history of this country and she lost and was upset about that. And I understand that."

It sounds tame, but that quip is a loaded insult. Still, for all the talk of Clinton's campaign "going high" when others go low, it's Sanders who's actually living up to that standard.

While Clinton has chosen to shirk accountability and stuff her post-defeat reflections with enough scapegoats to fill a zoo, Sanders has united with the DNC in an effort to rebuild the Democratic Party, of which he is not even a formal member (as Clinton bitterly observed). Though the DNC clearly favored Clinton in 2016, it's Sanders who has embarked on a cross-country unity tour with Chairman Tom Perez and worked to heal the gaping wounds of Democratic division opened during the campaign.

The former secretary of state, meanwhile, is still lobbing snide remarks in an effort to protect and repair her reputation, remarkably unaware of how that strategy is backfiring.

Let's not forget, by the way, a more cynical candidate than Sanders would never have dismissed Clinton's "damn emails" as a non-issue in the heat of a competitive campaign. Though Clinton should be grateful to him, she's carrying on now as though she believes she was entitled not to endure a serious primary battle for the nomination.

Though Clinton defeated him in the primary, Sanders is clobbering her when it comes to being a team player.

Emily Jashinsky is a commentary writer for the Washington Examiner.