Fashion has built in signals conveying the message being given by an individual or group's dress code. This message may include individual expression, marital status, income, occupation and social class, ethnic or political affiliations etc. Clothes also convey other social messages including claiming cultural identity or political affiliation.
Political activism has long existed since the beginning of time and along with it, political attire. From ancient Rome to Egypt, from the French Revolution through to the Russian Revolution, from World War 1 through to World War 2, from the Cold War through to the Civil Rights movements, fashion has played a significant role in reflecting the attitude and political stance of a particular group.
Since the symbolism of fashion often intersects with public figures in politics, their choice of garment hasn't been a matter of aesthetics, but of identity and strategy, for example, during the Russian revolution, the Bolsheviks and Mensheviks each had distinct uniforms and armstand to represent their factions.
The beatnik poets and writers of the post-World War II period railed against conformity and are usually remembered for their black clothing and jackets.
Another group that made a significant impact in art, culture, fashion and politics of the era was the Black Panthers. Not only did they influence the rise of anti-capitalist and anti-war movements, they also called for social awareness and gender equality - among other things. Their signature all black streetwear was intimately tied to the radical social movements of the time.
More recently, the BLM movement which employed similar stance, created and distributed BLM branded t-shirts and jackets in attempt to address police brutality the USA, Australia and all over the world.