Olsen scored his sixth and seventh goals of the season in the first half. It was his second multiple goal game of the season.
Christian Gomez and Fred added second half goals, as the United (13-6-3) won their sixth game in a row to solidify their hold on second place in the Eastern Conference.
FCD (11-8-3) took nine shots, including three on goal, but suffered its second loss in a row.
The Hoops lost a chance to move ahead of Chivas USA for second in the West.