If 'extremist' views are illegal, then the person who defines 'extremism' has the power to curtail free speech, freedom of religion, freedom of the press and freedom of association. This is the path to authoritarianism.

The government of Rishi Sunak was debating internally changing the definition of extremism to deal with Islamist and far-right extremism, but it was feared the changes could affect gender critical feminists and Christian activists opposed to abortion and Same-sex marriage in the United Kingdom.