“Show me a good loser and I’ll show you a loser.” The words are often attributed to famed Notre Dame football coach Knute Rockne. Judging from the ungraciousness that has characterized Hillary Clinton’s every public appearance since the November election, she has taken them to heart.

Friday’s commencement address at Wellesley—an attack on the man who defeated her—is only the latest outburst from a failed candidate, who has now vowed to take a leading position in the anti-Trump “resistance.” On the right these things provoke...