John Scott QC said Sheriff Charles Macnair QC had been wrong to not allow three witnesses to give evidence supporting Donnachie's argument that his protest had been a political one about the Israeli-Palestinian conflict, rather than an attack on Mr Reitblat's religious beliefs.
Donnachie was expelled from St Andrews after his conviction, but has since started studying at a new university. Mr Scott said characterising Donnachie as antisemitic was a "grave insult".
Lead prosecution lawyer Alex Prentice QC told the court that the evidence of the three witnesses would have been "irrelevant". He said an academic discussion on the politics of the Middle East would have been of no help in the trial or Sheriff Macnair's verdict.
The Lord Justice Clerk, Lord Gill, heard the appeal with Lord Mackay and Lord Bonomy. They questioned the relevance of the sheriff's decision.
The judges reserved their judgment and will give a ruling within three months.