At one point the House leadership (or possibly just the leadership of the Democrats in the House) forbade members from participating in this Colbert Report segment, because so many of them had been humiliated in doing so. I think Nancy Pelosi was on his show a few months ago and he asked her to relax that ban.
Aside from the congressperson’s confusion. The Dutch were most certainly involved in the slave trade. The first shipload of enslaved Africans arrived in what would become America aboard a Dutch ship in 1619.