From The Charity Commission:
Charities often play an important role in different parts of society and in different ways. This can include challenging held views and perceptions and undertaking high risk activities, which may involve encouraging free speech.
As such, many charities further their charitable aims by arranging meetings involving invited speakers and by distributing literature and other educational materials. In most cases, this causes no problems.
However, terrorists and those who encourage terrorism have been known to use charities to make their views known. These are risks which charity trustees need to be aware of and actively manage.