Felix Ngole, who says he was expressing a traditional Christian view and has complained that university bosses unfairly stopped him completing a postgraduate degree, raised his concern on Tuesday when trying to persuade appeal judges to overturn a ruling by Deputy High Court Judge Rowena Collins Rice.
Mr Ngole says his rights to freedom of speech and thought, enshrined in the European Convention on Human Rights, were breached when he was thrown off the course.
But lawyers representing the university say he showed "no insight" and said the decision to remove him from the course was fair.
They say Mr Ngole was studying for a professional qualification and say university bosses had to consider his fitness to practise.
Judge Collins Rice, who analysed the case at a High Court trial in 2017, ruled that university bosses had acted within the law.
She said freedom of religious discourse was a public good of great importance.
But she said social workers had considerable power over the lives of vulnerable people and said trust was a precious professional commodity.
Three appeal judges are now analysing Mr Ngole's challenge to Judge Collins Rice's ruling at a Court of Appeal hearing in London.
A lawyer leading Mr Ngole's legal team told Lord Justice Irwin, Lord Justice Haddon-Cave and Sir Jack Beatson that Judge Collins Rice's ruling raised an Orwellian spectre.
Barrister Paul Diamond said the ruling implied that professional regulators were entitled to regard an "expression of unpopular beliefs" on political, religious or philosophical issues as "undermining public confidence" in a profession and "thus" a breach of a professional code of conduct.
"It is by no means unusual for a professional regulatory framework to extend to students," he said in a written case outline.
"It can also be safely assumed that the majority of regulated professionals (and students) are users of social media.
"The judgment of Ms Collins Rice effectively gives professional regulators the powers of an Orwellian Thought Police over those six million people and abdicates the court's responsibility to protect their freedom of expression."
Barrister Sarah Hannett, who is leading Sheffield University's legal team, says Mr Ngole's appeal should be dismissed.
The appeal hearing is due to end on Wednesday.
Mr Ngole posted comments in 2015, judges have heard.
He was taking part in a debate on a Facebook page about Kim Davis, a state official in the US state of Kentucky, who refused to register same-sex marriages.
Mr Ngole said he had argued that Mrs Davis's position was based on the "Biblical view of same-sex marriage as a sin".
He said he was making a "genuine contribution" to an important public debate and said he was "entitled to express his religious views".
University bosses said he had posted comments on a publicly accessible Facebook page which were "derogatory of gay men and bisexuals".
The Thought Police feature in writer George Orwell's 1949 novel 1984 and are state secret police who investigate "thoughtcrime" - personal and political thoughts not approved by the ruling party.
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