In a democracy, the government are the servants of the people and rule by consent. There is no legitimate justification for violent protest in a democracy. Venting steam because you do not like a decision is not helpful or good for society. Impassioned debate and determination in the face of massive opposition is laudable but not if it is intended to cause a riot. So freedom of speech and action is only OK if it does not undermine the fundamental principles of the system.
The system of government in the UK has come under much criticism for;
Having a monarch albeit a constitutional one
Having a prime minister
Having a house of lords
Having an independent judiciary
Usually from republicans who feel that the US system is better or indeed the Russian system or just ill-informed anarchist or socialist
It is a shame that the system seems not to be fully explained to all those that come to live here or indeed grow up here. I accept it is complicated to grasp the nuance of a constitutional Monarchy or how an unelected second chamber works, and yes, I am sure that the arrangements can be improved but the basic concept, an elected government (built from the elected house of commons) proposes changes to our legal system which is voted for in parliament and then checked by experts who have the paid time to mull over the rules to see if they achieve and are feasible. And when enacted are kept in place by a legal system that is independent of government. Sounds good .. well that is what we have and then put in jeopardy with every riot or stupid act denying the “consent” of the basic agreement that fundamentally removes the needs to carry arms. Servants of the people means everything is done for the benefit of the electorate, fundamental requirement, anything done for self-interest has to disenfranchise that person.

We must protect the system we have to maintains the freedom of the country and its people entirely but we must have leaders that espouse the values we have not the values of the extremes we have.