Very true in many ways, typical Vietnamese people are quite nice and kind, but there are plenty of bad ruthless people and they prey on whoever is at hand. Lots of tricky people everywhere trying to rip you off and they are very visible to tourists such as tricky taxi drivers with fixed meters, tricky restaurants that overcharge you (that's why you always see Vietnamese people carefully checking the bill), tricky hotels where you book the room at one price but they charge you a higher price when you check out or don't let you leave, tricky tour agents that sell you one thing, but deliver a lower value than promised, etc, etc, etc, the list goes on. Bad people are always more visible and more noticeable than good people.
The other day, while walking, a tourist, a girl from Hong Kong stopped me to ask me some directions, we talked a little for a while and she told me what happened to her that morning: She was in Hoi An and at one point she asked a shop if she could use the toilet and asked how much, the shop owner, a woman, said: sure, its free. After using the toilet and as she was leaving, the woman stopped her and said: 100.000 vnd (5 usd) and didn't let her leave until she paid.
People like that, although a minority, ruin the reputation of Vietnam and Vietnamese people and there are many like that. It also doesn't help that lots of people in the service sector are rude and impolite and have no idea about proper customer service. There is a reason why a large proportion of tourist that have been in Vietnam say that they will never, ever come back to Vietnam. Vietnam has a lot to learn in those areas from Thailand.
This type of situation will slowly change, but it takes time; part of the problem is that tricky people / establishments get away with an small fine so they keep behaving the same way.
Oh no, there are much better places than bonpas in Danang.