The leader of the United States encouraging law enforcement and the military to shoot American citizens for looting, that's the line.
Which I agree with to some extent, you're not innocent of a crime because you convinced a person to harm another, just because you were too cowardly to get your hands dirty yourself.
But the US is rather famously not British, so I'm not sure if it's a relevant thing to add to the discussion.
The relevant kind of speech for "free expression" is that which seeks to express an idea/opinion/belief of the speaker.
That isn't criminalised in the UK as far as I'm aware, and would fall under the EHCR protections in any case which are in UK law as the human rights act.