I think it’s OK to bring politics into the workplace. I discuss Brexit, elections, Boris Johnson, Jeremy Corbyn, Donald Trump, etc, with those of my colleagues that want to discuss it when they want to discuss it. I agree with some of them, disagree with others.

I think the key difference is, you aren't trying to paint those who disagree with you or even refuse participation in such discussions as members of some axis of evil. Unfortunately, it is only possible if the overall culture of your company is conductive to that, as opposed to the monoculture of "if you aren't as enthusiastic about this topic as me, then you are the enemy".

If only the activists were mature enough to approach it this way.

Yes, same here. You can discuss politics at work without making the other person seem evil because they disagree with you. You shouldn't be doing that in a work place - everyone needs to work together to make things happen, and you will be around people with obviously different viewpoints than you.

Totally wrong. Haven't you heard people claim "everything is political"?

Have you ever heard someone say that AND say you should keep politics out of the workplace?