We must not let the extremists intimidate us into silence. Things like this need to be talked about in the public square.
'Let us not forget that violence does not and cannot flourish by itself; it is inevitably intertwined with lying. Between them there is the closest, the most profound and natural bond: nothing screens violence except lies, and the only way lies can hold out is by violence. Whoever has announced violence as his method must inevitably choose lies as his principle....' -- Alexander Solzhenitsyn
This is why the truth is so important. Lies ruin lives.
See also The Islamic Reformation Is Here—and You Won't Like It by Raymond Ibrahim.1
If you think you know someone with extreme views, what should you do? First of all I'd suggest that you talk with him (or her) and find out what they believe. (If I was concerned about my safety I'd do it with a friend in a public place.) If you have misjudged the person, you will not know if you have or not if you don't talk with them. And you certainly won't help someone with extremist views if you ignore them. Ignoring an extremist will make him more extreme; he'll stay fixed in his ways and he'll feel like he has to take more extreme measures to get through to you.
Let the extremists speak, and then use your own freedom of speech to counter their arguments. If your side has the truth, your side will win the debate. This is important, because when people feel like they are being ignored, when they feel like the law is being used to silence them, they often turn to violence. (This is what happened with Anders Breivik (see video below). He believed talking to people was a waste of time, so he used violence to try and get through to politicians.) If you do not give people the freedom to speak their minds—without fear of prosecution—society will become more and more polarised. This is why right-wing parties all across the western world are growing in popularity. A large percentage of people believe their freedom of speech is being suppressed through the use of lawfare. (See Tommy Robinson's film 'Silenced.' The law is already used to suppress freedom of speech in communist countries and the Islamic world, do we really want that kind of suppression in the west? See Mark Durie's book The Third Choice.)
If you want to influence how an extremist thinks, talk with him. Reflect back to him what he is saying and ask penetrating questions. Yes it's difficult, but what options do we have on the individual level?
This is important, because as the videos above show, Britain is in trouble. See “Ex-Marine: We Lost in Afghanistan and We're Losing at Home Too” on Triggernometry.
So what exactly is an extremist?
Here is my definition of an extremist and how governments should address the issue. Read on
1. Muslims do not have to convince non-Muslims that Islam is peaceful—we are not the ones committing terrorist attacks in the name of Islam. It’s the responsibility of the imams to convince Muslims that Islam condemns the violent form of jihad. See Jihad Exposed in America by the YouTube channel 'PatristicNectarFilms.' For a list of terrorist attacks around the world—which is constantly being updated—see https://www.thereligionofpeace.com.
Imams also need to make it clear where they stand on sharia. And if they do support it, how can it fit in the modern world? See Mark Durie's article "Australian Imams Stand up for Shariah."
Recommended Reading
Sword and Scimitar: Fourteen Centuries of War between Islam and the West by Raymond Ibrahim