Morrison struck in the 4-3 home defeat.
He said: "It was a bit mad. The first-half was one of the craziest 45 minutes of football I've ever played in.
"We came off at half-time feeling comfortable as there wasn't much going on. The first goal went in at the front post and the second was a penalty.
"We felt comfortable in our shape and in the second half they sat in their shape making it hard for us to break them down.
"I think we can take away a lot as they're one of the best teams in the world. I would exchange that goal for a point or three any day of the week.
"It's nice to be able to say I've scored against Man United. They have some of the best players in the world and you know if they get a chance then they will score."