The 64-year-old former Barcelona, Bayern Munich and Ajax Amsterdam supremo has been the target of strong media criticism following United's run of eight matches without a victory in all competitions.
Van Gaal, however, hailed the "fantastic" reaction of the United supporters.
"I've had bad periods at all my clubs and I have to say the best fans are here at Manchester United," he told reporters ahead of the weekend's home game with Swansea City.
"In such a difficult period, they were applauding the performance of the players and that's fantastic."
United have slipped to sixth in the Premier League, nine points behind joint leaders Arsenal and Leicester City, and Van Gaal is aware his team have an urgent need to arrest their slide.
"We have to get points otherwise the gap is too big," the Dutchman said. "We have to work, prepare the game, perform and then evaluate the game again.
"That is, of course, much more difficult when you don't win than when you win. We need to win because we want to be at the top of the league, not the middle."
United dominated their 0-0 draw with champions Chelsea at Old Trafford on Monday but were again undone by sub-standard finishing from their attacking players.
"We've had many games like that," said Van Gaal, who has also twice coached the Dutch national team. "The way we've played this season, we're more or less always the dominant team.
"Certainly at home we have played many, many matches like that but we don't score and that is our problem ... goals are the most important thing."
