While they have indeed been denied entry I do struggle to believe that THAT letter isn't fake. If it is real then the Home Office needs to start sacking people that can't use correct English in public correspondence.
Tommy Robinson ( or whatever he wants to call himself today ) does indeed have the right to question the actions and beliefs you mention. The problem being that he doesn't tend to question equally appalling beliefs and behaviours by other faiths - he just appears to have a problem with a faith...