One of our members commented concisely and incisively in our private discussion group (slightly revised here):
In Calvinism God cannot see into the future. He only knows what will happen because He will make it all happen. This again leads to the inevitable conclusion that God is the cause and author of all sin and evil in the universe. He makes sin and evil happen just as He makes everything else happen. One cannot appeal to “secondary causes” because God must make them happen as well. God directly controls everything in accordance with His all encompassing eternal decree. Some Calvinists find the Calvinist account of foreknowledge compelling precisely because it explains how God can foreknow the future, while the Arminian account doesn’t care so much how God can know the future, satisfied simply to affirm that God is capable of doing such things, just as He can create out of nothing, etc.