Violence isn’t speech. Calling Molotov cocktailing a street “protest” is absurd. It’s effectively armed conflict.
How do you think Franco got in power? By peacefully using his free speech rights and persuasive speeches? How do you think he stayed in power for all those decades? Do you think some people's free speech rights and avenues of protest might have been a teensy tiny bit curtailed?
And of course it's armed conflict. But the point is that it's armed conflict against a fascist dictatorship killing over 100,000 civilians by most estimates -- which is what makes it considered legitimate violent protest by many people.