take a stand
Adopt a firm position about an issue, as in She was more than willing to take a stand on abortion rights. This idiom alludes to the military sense of stand, “hold one's ground against an enemy.” [Mid-1800s] Also see make a stand.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.