Story highlights "Dr. Song's comment was inappropriate and insensitive," Sanders tweeted

Song made the remark at a Sanders rally in Washington Park Wednesday

Washington (CNN) Vermont Sen. Bernie Sanders said Thursday a supporter's use of the phrase "corporate Democratic whores" ahead of his speech at a campaign rally in New York City's Washington Square Park was "inappropriate and insensitive."

Dr. Paul Song, railing against the relationship between politicians and corporations before Sanders' supporters on Wednesday, said, "Medicare-for-all will never happen if we continue to elect corporate Democratic whores who are beholden to big pharma and the private insurance industry instead of us."

A law enforcement official estimated the crowd size at 15,000, though the campaign cited a a higher number of attendees -- 27,000, according to a press release.

Some critics thought it was a swipe at Sanders' rival for the Democratic presidential nomination, Hillary Clinton.

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