Holloway refused to blame referee Jon Moss following his decision to award a penalty to the home side after Kagisho Dikgacoi was dismissed for an innocuous challenge on Ashley Young.
The Palace boss, who was fined £18,000 for berating the referee after his side's opening game against Tottenham, acknowledged the pressure on match officials at Old Trafford is intense.
"I am glad I don't have to do it," said Holloway.
"It is a weird feeling being up in the crowd and see how partisan their fans are.
"They were shouting for everything.
"They were shouting for stuff before we even kicked off. If you are in the middle and you have that whistle, it is very hard."
Young was cautioned for simulation before the sending-off when he threw himself to the ground after tangling with Dikgacoi.
Manchester United manager David Moyes revealed he will speak to the player about the incident but Holloway resisted the temptation to publicly condemn the England international.
"I don't talk about other people's players," said Holloway.
"If you want to meet me down the pub later on I will tell you exactly what I think."