Already trailing by two goals the visitors conceded a penalty and had Lee Molyneaux sent off shortly before half time. Danny Kedwell converted the spot kick and the National South hosts added another four goals after the break.
Meanwhile, Petersfield Town also lost away after enduring another dismal afternoon in the Southern League as they sunk to a 4-1 defeat against Bedford Town.
In the Wessex Premier ten-man AFC Portchester came from behind to beat Amesbury Town 2-1 at the Blanchard Wells Stadium.
The home side had Josh Warren sent off after five minutes and fell behind to a 27th minute penalty.
Goals from Jake Peppal and Dale Mason won the game for the Royals.
Horndean beat Lymington Town 2-1 at Five Heads Park while Fareham Town and Bashley fought out a 0-0 draw at Cams Alders.
League leaders Moneyfields suffered a surprise 3-2 defeat against Bemerton Heath Harlequins at Dover Road.
In Division One, Baffins Milton Rovers crashed to a 4-2 home defeat against Romsey Town.
United Services Portsmouth slipped to a 3-2 defeat at AFC Stoneham.