You have to be careful about how you phrase that argument. Voting for something a second time isn't automatically undemocratic. For example, we'd support another a referendum on abortion despite that it has been rejected in the past. Conditions, opinions and outlooks have changed since then. The undemocratic nature of Lisbon 2 isn't just holding another referendum in itself, it's to the scaremongering nature of the Yes campaign that has manipulated public opinion and that this isn't the first time that they've attempted to push through a referendum twice.