In a recent holiday to Vietnam the guide asked the nine of us for tips 'upfront' to make it easy. As the tour literature said tipping was optional we declined and tipped ourselves. The tour guide must have taken offence as the next day on a visit to a museum she left without us and also told the other guests we had not given her money for tips alienating these guests against us, some were abusive. (I am almost certail almost all the money was kept by the guide).
I complained to the tour company and they replied 'they are not responsible for other guest behavoir'
I believe we have been subject to a sort of blackmail, any advise please.