It is also unprofessional if you fall apart like that no matter whether the opponent is called Liverpool or not. Conceding six goals in one half is even worse than conceding three goals in each half. Imagine how many things have to go wrong and how bad the players' attitude and motivation has to be in order for the opponent to be able to score six goals. That is a no go in my opinion.
I do not think it is worse because it is easier to get overrun in a small time but they played good in the 1st half and they looked better then Liverpool. Manchester United nearly scored a couple of times in the first half and it is only because Liverpool scored before half time that they had confidence and Manchester United never recovered from the goal before the half time. The result was many days ago now and I think it is time we talk about the next fixture and how Manchester United will react I think we will see a reaction and they will show that they have good mentality to win the next game. Ok that is a good point but still, getting overrun is what you would say even when you concede three goals in 20 minutes. I would say that already counts like getting overrun. But when you are Manchester United and you concede one goal every 7.5 minutes for an entire half, oh oh...
But it's true and it has happened to other clubs as well. Even though it is not the domestic league, but it is a prime example of what you are saying in terms of getting overrun is the game between Barcelona and Bayern. I could never trust my eyes when it was 2-8 Barcelona vs. Bayern. Events like that can happen and there are two sides of the medal. While Manchester United is suffering from it on that day, Liverpool gained back its confidence and is perhaps going to make the impossible possible.
For now it is all about the game against all about the game against Betis.