... through to the fourth round of the FA Cup and suggested that traffic around Old Trafford - rather than apathy - was one of the reasons why many supporters left before the end of the 1-0 win over Sheffield United.
Thousands of fans streamed out of the stadium on Saturday evening before the end of the third round tie, which the hosts won thanks to a penalty three minutes into stoppage time from Wayne Rooney.
United did not register a shot on target against the Sky Bet League 1 side until the 69th minute and were booed off at half-time.
But Van Gaal insists supporters should be happy with the way their team have returned to winning ways in recent weeks following a run of eight matches without victory.
The United manager said: "You have to be happy as a Manchester United fan that we are in next round and we have won the last two games."
When asked why many had left the stadium early, Van Gaal said: "They are not thinking that we would score, I think, and maybe also because of the traffic that they leave the stadium a few minutes early.
"There are many reasons."
Van Gaal added: "I think the fans have supported our team. It is not an easy time now, so I think the fans were there also.
"How many stadiums were like our stadium, full, I think?
"You can mention how they leave, but you can also mention how they come to the stadium to watch this FA Cup match."
Paul Scholes tore into Van Gaal after the final whistle, claiming the players and the manager looked "bored".
Van Gaal refused to respond to the outspoken former United midfielder at his press conference on Monday.
The Dutchman said: "What do I have to do now? React to Paul Scholes? Do you want that?"