Siddique, a vocal critic of what he describes as Israel's record of human-rights abuses in the Palestinian territories, maintains that he has been misunderstood in the fallout from a Labor Day weekend protest in Washington.
"I am against Israel - not against Jews," he said.
Lincoln University officials have since distanced themselves from the professor's personal views.
On Tuesday, the Christian Broadcasting Network aired video of Siddique, an associate professor of English and literature, speaking on Labor Day, saying: "We must stand united to defeat, to destroy, to dismantle Israel - if possible by peaceful means."
Backed by a crowd of cheering protesters, he continued: "Dear brothers and sisters, unite and rise up against this hydra-headed monster which calls itself Zionism."
The video and additional articles in which Siddique questions the validity of the Holocaust have since drawn criticism from pro-Israel groups, who question his continued employment at the state-funded university and have mounted a campaign against him.
State Sens. Daylin Leach (D., Montgomery) and Anthony Hardy Williams (D., Phila.) joined those ranks Wednesday in a letter asking Lincoln president Ivory Nelson to ensure the professor's "anti-Semitic diatribes" had not made their way into Lincoln's classrooms.
They cited a recently passed Senate resolution denouncing hate speech on the part of state employees and faculty at state-funded universities, including Lincoln, the nation's oldest historically black university.
"We support academic freedom and certainly a professor has the right to criticize Israel, or any other entity or policy he wishes," they wrote. "However . . . the Holocaust is not a theory or opinion. It is historically documented fact, denied only by those with a hateful or anti-Semitic agenda."
The university responded in a statement Thursday saying it had not been made aware of any instance in which Siddique's views were taught in his classes or shared in any public forums on campus.
Siddique, a Muslim originally from Pakistan, said Thursday that he was used to people questioning his personal views. Since the CBN story aired, phone calls and e-mails from critics have poured in.
"It has become so abusive even my wife is beginning to be worried," he said. "If I were not tenured I might be under some pressure to leave."
But he said he would continue to speak out in his free time, no matter how others might feel about those statements.
"I don't believe in laying low," he said.
Contact staff writer Jeremy Roebuck at 610-313-8212 or firstname.lastname@example.org.