Stephen Hawking has been subject to vile abuse targeting his disability after it was announced he is planning to boycott a conference in Israel, hosted by the country's president Shimon Peres.
The move has outraged organisers of the conference and Israeli academics, but delighted Palestinian human rights campaigners.
"The academic boycott against Israel is in our view outrageous and improper, certainly for someone for whom the spirit of liberty lies at the basis of his human and academic mission," conference chairman Israel Maimon said in a statement.
Some of the ugliest responses to the boycott came on social media, with several accusing Hawking's singling out of Israel for boycott as "anti-Semitism" and making distasteful comments about his disability.
Hawking's condition worsened recently, causing him to struggle to communicate. The 71-year-old was diagnosed with motor neurone disease aged 21. He is an exceptional case, having survived for more than 40 years, despite doctors giving him just two years to live when first diagnosed.
The celebrated physicist withdrew from the conference, approving a statement in his name distributed by the British Committee for the Universities in Palestine, confirming his withdrawal was for political reasons, and not for health reasons.
The University of Cambridge had alleged on Wednesday that his reasons for non-attendance were purely health related, but was later forced into a volte-face, and agreed the reason was indeed political.
The Palestinian Solidarity Campaign later released the full letter from Hawking to conference organisers, which read: "I accepted the invitation to the Presidential Conference with the intention that this would not only allow me to express my opinion on the prospects for a peace settlement but also because it would allow me to lecture on the West Bank.
"However, I have received a number of emails from Palestinian academics. They are unanimous that I should respect the boycott. In view of this, I must withdraw from the conference. Had I attended, I would have stated my opinion that the policy of the present Israeli government is likely to lead to disaster."
Hawking visited Israel in 2006, giving public lectures at Israeli and Palestinian universities as the guest of the British embassy in Tel Aviv.