Lord Simon Woolley, principal of Homerton College at the University of Cambridge, told the vigil that when he met with Arday last week, the academic told him he felt that critics were "hounding me to death".
Filmmaker and activist Misan Harriman told the vigil: "The legacy media crossed every line in the treatment of Jason.
"Imagine being so lost in the business of cruelty that you relish hurting another human for sport, with your own poison pen."
He added: "Jason should still be here today."
The University of Cambridge initially said claims of plagiarism regarding Arday's thesis and some journal publications had been investigated by Liverpool John Moores University (LJMU) and the journals in question.
LJMU - which awarded Arday his PhD in 2015 - concluded that he had not plagiarised work.
But last week, Cambridge announced an independent investigation into his appointment.
Arday, 41, was found dead at an address in south London, on Friday. He had resigned as a Cambridge professor of sociology of education on 5 August, saying his resignation should not "be mistaken for an acceptance of the narratives that have surrounded me".
Monday's vigil came as more than 90,000 people signed a Good Law Project petition seeking an inquiry into media coverage of Arday.
Earlier, Cambridge University's chancellor criticised the "racist feeding frenzy" around Arday in the weeks before his death.
Speaking publicly for the first time on the row, Lord Chris Smith said academic integrity could be upheld while questioning Arday's treatment.
In a statement, he said: "I do believe it is possible to hold to two principles at the same time: to believe in the importance of academic integrity, and where criticisms of plagiarism arise, about any academic, whoever they are, ensure that they are rigorously investigated.
"And also to refuse to join in a racist feeding frenzy over a particular academic."

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