This man’s behaviour is clearly unacceptable and quite possibly illegal. As carriers of the Message of Islam we are not called to condemn people but to bring the Truth about the One God whom the Qur’an calls the Most Compassionate, Most Merciful.
Abu Huraira reported: It was said, “O Messenger of God, pray against the idolaters!” The Messenger of God, peace and blessings be upon him, said, “Verily, I was not sent to invoke curses, but rather I was only sent as mercy.”
Source: Ṣaḥīḥ Muslim 2599
To those brothers who might question my publicly rebuking this individual and condemning his behaviour we have to consider the following. In our society today it is no longer enough to privately censure bad behaviour which is committed in public and filmed for all to see. We must speak out to explain that it is utterly unIslamic and contrary to Islamic teaching. Our enemies will make much of this incident so we must clearly disasociate ourselves from the evil that we see done in the name of the Noble faith of Islam.
Finally, I note that bad behaviour by Christians occurs regularly at Speakers’ Corner. They too have issues to address.