What term describes someone who is combative and aggressive in support of a political or social cause?

The term that encompasses a person who is combative and aggressive in support of a political or social cause is "militant." This term specifically denotes an individual who is not only active in promoting a cause but also adopts a confrontational and often aggressive approach to advocacy.

"Militant" implies a readiness to engage in conflict or take direct action, which can include protests, demonstrations, or even more extreme measures to assert their beliefs. The usage of this term conveys a sense of intensity and fervor in their efforts to propagate their viewpoint, often placing them at the forefront of contentious social or political issues.

In contrast, while "activist" broadly refers to someone who actively engages in advocacy for a cause, it does not inherently imply a combative stance. "Protester" similarly indicates involvement in demonstrations against issues but lacks the aggressive connotation associated with "militant." "Campaigner" denotes someone who supports a cause through organized efforts or campaigns, but it also does not suggest the same level of confrontation or aggression as "militant." Therefore, "militant" is the most accurate term to describe someone who exhibits a combative and aggressive demeanor in support of their beliefs.