In Britain, the US Constitution is irrelevant (How I wish that Scottish Law was deemed irrelevant in the US, but that's another story)
However, in the US these terrorists, besides arson and terrorism charges, would be in violation of US Code Title 18 section 241:
§ 241. Conspiracy against rights
If two or more persons conspire to injure, oppress, threaten, or intimidate any person in any State, Territory, Commonwealth, Possession, or District in the free exercise or enjoyment of any right or privilege secured to him by the Constitution or laws of the United States, or because of his having so exercised the same; orIf two or more persons go in disguise on the highway, or on the premises of another, with intent to prevent or hinder his free exercise or enjoyment of any right or privilege so secured—
They shall be fined under this title or imprisoned not more than ten years, or both; and if death results from the acts committed in violation of this section or if such acts include kidnapping or an attempt to kidnap, aggravated sexual abuse or an attempt to commit aggravated sexual abuse, or an attempt to kill, they shall be fined under this title or imprisoned for any term of years or for life, or both, or may be sentenced to death.
There’s no doubt that burning someone’s house is against the law (apparently even in Britain, who’da thunkit?).
However, that section 241 is very interesting. It seems like it would be useful in a lot of situations of Moslem pressure or intimidation that fall short of being actionable under other statutes.