protester:
(plural: ‘protesters‘; for the right pronunciation, please click here)
‘to protest’ = to express one’s opinion, objection, dislike, anger or dissent openly, usually using loud voice and strong words

protesters protesting
a person who expresses his/her opposition, dislike, objection or dissent to another person or to a policy, law, rule, etc., openly in public, usually along with others in a group;
a demonstrator; a dissenter,

protesters turning violent
e.g.
Several protesters of ‘abortion law’ were arrested and later released.
The streets of several towns and cities in most Islamic nations these days are crowded with anti-government protesters and the governments are using different methods, including force to control those protesters.
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