Final answer:
Bull Connor, the Alabama police commissioner in Birmingham in 1963, became infamous for his violent actions against civil rights protesters, using fire hoses and police dogs. His actions were pivotal in garnering nationwide support for the civil rights movement.
Step-by-step explanation:
The Alabama police commissioner who horrified the nation with his violence against civil rights protestors was Bull Connor. In 1963, during a peaceful protest in Birmingham, Connor ordered the use of high-pressure fire hoses and police dogs against demonstrators, including children. The nation watched in shock as the brutality unfolded on television, with images that became emblematic of the civil rights struggle. These aggressive tactics used by Bull Connor and his police force contributed to a national outcry and stronger support for civil rights legislation.