Harvard Law professor emeritus Alan Dershowitz called the school's decision to drop Ronald Sullivan Jr. from his role as dean of a residential house after he joined Harvey Weinstein's legal defense team “the new McCarthyism.”

Dershowitz reacted in a series of tweets Sunday, “The new McCarthyism comes to Harvard. The firing of Dean Sullivan reminds me of the bad old days when lawyers were fired for representing communists, gay people, civil rights demonstrators and women seeking abortions.”

Sullivan, a Harvard Law professor, signed on to become one of Weinstein's lawyers in January, which sparked outrage from many students at Winthrop House - the Harvard residential college where Sullivan has worked since 2009. He has lived and supervised students at the house.

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In a written statement Saturday, Harvard College Dean Rakesh Khurana said he would not renew the appointments of Ronald Sullivan and his wife, Stephanie Robinson, a law school lecturer, when their term ends on June 30, citing “numerous” concerns about the climate at Winthrop House, which he described as “serious.”

The couple became the first black faculty deans in Harvard history when they took their positions at Winthrop ten years ago.

Some students and faculty members have criticized Sullivan's decision to represent Weinstein and his response to students' concerns.

In February, more than 50 students protested, demanding that Sullivan resign or be removed as dean of Winthrop House, according to the university’s newspaper.

The next month, graffiti calling for Sullivan's resignation appeared on a Harvard building.

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Khurana called the situation regrettable and said efforts to improve the climate were ineffective.

A few minutes after his initial tweet, Dershowitz wrote, “This may be the worst violation of academic freedom during my 55 year association with Harvard. Any student who feels 'unsafe' in the presence of Dean Sullivan and his wife does not belong at a university.”

He added, “'Feeling unsafe' is the new mantra of the new McCarthyism. It’s an excuse for firing anyone, from a Republican to a Muslim,” invoking Sen. Joseph McCarthy, the Wisconsin Republican linked to the post-World War II "Red Scare." McCarthy served in the Senate from 1947 until his death in 1957.

Later, he tweeted, “If the students who demanded the firing of Sullivan had been around in 1776, John Adams would have been fired as an author of the Declaration because he made them feel unsafe for representing the Brits accused of the Boston Massacre. Shame on these student McCarthyites.”

Harvard did not immediately respond to Fox News’ request for comment on Dershowitz's reaction.

Sullivan and Robinson said in an email that they were "surprised" and "dismayed" by the Ivy League school's decision not to renew their appointments as residential deans. They said Harvard unilaterally ended discussions that they believed had been progressing.

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Weinstein is charged with raping an unidentified female acquaintance in his hotel room in 2013 and performing a forcible sex act on a different woman in 2006.

Weinstein has denied all allegations of nonconsensual sex. He pleaded not guilty and was freed on $1 million bail. His trial is scheduled to begin June 3.

The Associated Press contributed to this report.