What a sewer the UK has become. Only anti-Christian hate allowed.
Pamela Geller and Robert Spencer co-founded anti-Muslim group Stop Islamization of America.
They were due to speak at an English Defence League march in Woolwich, where Drummer Lee Rigby was killed.
A government spokesman said individuals whose presence "is not conducive to the public good" could be excluded by the home secretary.
He added: "We condemn all those whose behaviours and views run counter to our shared values and will not stand for extremism in any form."