Demonstrant vs. Protestierender
Both Demonstrant and Protestierender translate to protester or demonstrator in English, but they differ in scope and context. While a Demonstrant is specifically someone taking part in an organized public street demonstration or rally, a Protestierender is a broader term for anyone actively expressing objection or dissent, whether in a public march, a private meeting, or through a written complaint.
Demonstrant
A Demonstrant is a person who physically participates in an organized public demonstration, march, or rally to express a collective political or social opinion.
Ein einzelner Demonstrant blockierte den Eingang zum Rathaus.
(A single demonstrator blocked the entrance to the city hall.)
Viele Demonstranten zogen friedlich durch die Innenstadt.
(Many demonstrators marched peacefully through the city center.)
Der Demonstrant hielt ein großes Schild mit der Aufschrift Frieden in die Höhe.
(The protester held up a large sign that read peace.)
Die Polizei forderte jeden Demonstranten auf, den Platz zu verlassen.
(The police ordered every demonstrator to leave the square.)
Als Demonstrant muss man sich an die vorgegebenen Routen der Versammlung halten.
(As a demonstrator, one must stick to the designated routes of the assembly.)
Protestierender
A Protestierender is anyone who is actively protesting or objecting to something in a general sense, which can include public marches but also verbal objections, written complaints, or individual acts of defiance in everyday situations.
Ein lautstarker Protestierender unterbrach die Rede des Bürgermeisters im Saal.
(A vocal protester interrupted the mayor's speech in the hall.)
Jeder Protestierende durfte sein Anliegen vor dem Ausschuss vortragen.
(Every protesting individual was allowed to present their concern to the committee.)
Als einsamer Protestierender weigerte er sich konsequent, das neue Vertragswerk zu unterschreiben.
(As a lone protester, he consistently refused to sign the new contract.)
Die Gruppe der Protestierenden umfasste unzufriedene Kunden und ehemalige Mitarbeiter.
(The group of protesters included dissatisfied customers and former employees.)
Der Protestierende verfasste einen offenen Brief an das Management der Firma.
(The protester wrote an open letter to the company's management.)
Summary
In short, every Demonstrant is usually a Protestierender, but not every Protestierender is a Demonstrant. You use Demonstrant when talking about physical crowds and organized rallies on the streets, and Protestierender when focusing on the act of objecting, regardless of whether it happens outdoors, in a boardroom, or via correspondence.