In what way was the sacking handled poorly? Another club would have sacked him in December when we got dicked by Stoke. Or the way we crashed out of the CL. Heck, there were arguments for sacking him for finishing 4th in a season with no European football, which would have been the case had we been as ruthless as other big clubs like Madrid or Chelsea.
Instead, we gave him time, Ed even accepted a 0-0 draw against Chelsea in Jan as a turning point. Then, he ensured that van Gaal was given time to win the FA Cup and allowed him to go out on a high. The club also released a classy statement thanking van Gaal, though to be honest, he deserved little thanks for putting us through that shite.
If talking to Mourinho behind van Gaal's back is a crime, then I dunno what you would call the operations of other clubs who sack managers more ruthlessly than we did.
If we announced Mourinho was taking over in January, the players would down tools. van Gaal's just bullshitting about that, he would never have taken that kindly.