All of the "union" states that had regions with slavery were the SAME places that were sympathetic to the "confederate cause" during the civil war...especially Maryland as you pointed out.
Even the "yankee" areas that did NOT have slavery and were pro-confederate had very pro-slavery feelings...for instance the "Little Egypt" region of southern Illinois. That was a bastion of former slave owners who serious mulled over seceding from the rest of Illinois during the civil war. They would have still had slavery if Illinois hadn't outlawed it in 1828.
Funny how that works, eh? All those "northerner" areas supported the confederacy also though slavery was a great system. Must be a coincidence, eh? I'm sure the fact they were pro-slavery and pro-confederate was completely unrelated and just mentioned by evil yankees to make "the south" look bad. Riiiiiiiiight.
Not always the case. For example, General Sherman supported slavery and said so many times... he just opposed secession. In those border states where there was southern sympathy, the North just declared martial law... and would lock up local officials just on the suspicion that they sympathized with the south.
It's funny, these "neo-confederates" as you call them kept John Kerry out of the White House... yet those of you who have been indoctrinated by the left on this issue continue to bash them.