Cynical, cynical me. Pickett's account of Fredericksburg was written at the height of the sentimental age in America, when writers in a pop Romantic daze routinely emphasized noble idealism at the expense of sordid reality. (The "Custer myth" is an apt example.)

My reading of human nature suggests that those Confederate Irishmen were more likely cheering at the effectiveness of their own fire on the Union Army, blowing gaps in the formations even as they approached to within "25 paces of the wall," than at the bravery the enemy exhibited.

Sympathy for an enemy's courage and losses usually comes after the battle - if it comes at all. Cheering an advancing enemy coming straight for you while his cannon fire rains down on your head strikes me as too idealistic for actual human beings.

BTW, the movie "Gods and Generals" (a 19th C. film if ever there was one) did a great job with the battle of Fredericksburg.