I think the woman's comments about burning down a mosque with people in it was absolutely reprehensible. Bearing in mind places of worship in previous times have been set alight with people in them. The Jews during the Middle Ages who took refuge in a church in York perished, more recently Nazis locked French villagers in a church and set it on fire. Such individuals in the time of SM who advocate killing innocent people in such a horrible way should be made to face the consequences of what they are saying, I'm not sure what the appropriate sentence should be, but such sentiments surely constitute a hate crime.
However, some time ago it was a known fact that certain mosques hosted Iman's who gave hate speeches. Channel 4 Dispatches programme went under cover and their covert filming disclosed such rhetoric that advocated violence towards Gay people, Jews and Christians. The message was "kill the infidel" Were prison sentences received at the time? I don't think so, but I could swear to that. I do wonder now the heat is more focused on right wing extremism, and I'm not denying that is also a threat, whether those clerics who preach hate are still under surveillance, because as we know from recent history they have inspired the young, impressionable and disaffected to carry out acts of extreme terror taking many lives and leaving others permanently maimed.