Not everybody is an expert on EU finances or what the EU does, and people can only go on their experiences and beliefs.
If their experience and belief tells them that they are being held back, or that things just aren't fair whilst others profit and benefit and laud it over them, then they are not going to be happy and will say 'stuff this, I say no!'
Myself, I would have been okay with the EU saying 'okay lets get a sense of perspective, and rather than lose the UK can we help them in some way to take some off the pressure off?' When a family member is going through trouble, do you say 'let us help you, please let's talk' or do you say 'we're not interested'. Most people would try to help, wherever possible, but as with a lot of things today you are either in one camp or another - you can't be in both or neither, according to those with loud voices.