"Waving the Bloody Shirt"
That was a technique used by Reconstructionists to bring the south to tow after the civil war.
Congressmen LITERALLY waved the bloody shirt of a Union soldier to remind Congress of the horror that the south had wrought upon the Union. It was very effective.
Trump's defense thinks this is something bad....it isn't...the country needs to see the bloody results of Trump's insurrection and we NEED TO WAVE THE BLOODY SHIRT so that nobody in the country can deny the treasonous effects of Trump's actions.
...Reconstructionist efforts and arguments as mere political histrionics, playing on emotions for mere political advantage.
The phrases gained popularity with a fictitious incident in which Representative, and former Union general, Benjamin Butler of Massachusetts, while making a speech on the floor of the U.S. House of Representatives in April of 1871, allegedly held up a shirt stained with the blood of a Reconstruction Era carpetbagger who had been whipped by the Ku Klux Klan. While Butler did give a speech condemning the Klan, he never waved anyone's bloody shirt. White Southerners mocked Butler, using the fiction of him having "waved the bloody shirt", to dismiss Klan thuggery and other atrocities committed against freed slaves and Republicans.
The Red Shirts, a defunct 19th-century white supremacist paramilitary organization, took their name from the term.
In current usage, the terms, often abbreviated bloody shirt, are used more broadly to refer to any effort to stir up partisan animosity.
Then as now, it was an effort to pretend they were the real victims.
I was raised in the south and had an 8th grade American History teacher who derided the "Yankees" for waving the bloody shirt to mete out punishment to the south...this was BEFORE desegregation was implemented in our community.
Thanks for your perspective.