Thaddeus Stevens was a US Congressman, not Senator.
There is no record of Confederate troops destroying Union steel mills, whether they belonged to Stevens or anybody else.
Confederate troops did invade and destroy or seize property in Chambersburg, Pennsylvania three different times -- in October 1862, June-July 1863 and July-August 1864 (none of those raids lasted longer than a few days):
Indeed, "Remember Chambersburg" became a battle-cry of Union troops under General Sherman in Georgia.
And forgive my confusions about the destruction of steel mills rather than warehouses and railroad infrastructure.
The point is that the Confederates wrecked military and infrastructure targets, not farms, villages and towns in their path as Sherman did. That even included the Early raid on Chambersburg in 1864 as the only political target which Early's cavalry went out of their way to destroy was the home of prominent abolitionist newspaper editor. Quite the contrast to Sherman's army who went after everything, including the homes of widows and orphans.
That being said, my original comments were fully supportive of union monuments on battlefields in the south as I pointed our that there were no shortage of confederate monuments on this side of the Mason-Dixon line.