To expect people to behave 'properly' at the theatre?

You are completely right to be cross. Those people were totally out of order and being very selfish.

I remember being refunded by our local cinema because of disruptive behaviour of other people. A nice gesture. They were also asked to leave.

I should have added in my rant that DD1 asked the manager why the advertising hadn't said that it was an audience participation event. The manager said that it wasn't, so we complained about their 'policing' of the auditorium but there was no offer of a refund or more tickets. Still

I've booked the next one!! In April, we are going to see Sadlers Wells 'West Side Story' in Birmingham. [bliss]

We don't do the cinema for the same reason; but we do sometimes go to Flix in the Stix in the village hall, where the behaviour is civilised.

I would have complained to the manager if I were you kitty and said you would not be back.

No, you are not being unreasonable. Perhaps there should be a ban on alcohol except for a glass during the interval.

My daughter and her husband stopped going to the cinema for the same reason. We're lucky at our cinema as they don't sell popcorn or anything like that and people are pretty good at turning their phones off [one of my bugbears is seeing the lights from peoples phones when I'm trying to concentrate on a film]. Somebody did talk slightly into the beginning of the last film we saw, so I can understand how annoyed you were, because I felt myself getting all wound up [he didn't continue, thankfully]. At least you can sway your daughters towards a production where this is less likely to happen next time . Perhaps you should write to the theatre and tell them they should call it 'singalongadirtydancing' next time.