People some to ignore the fact that in 1972 the public weren't asked of we wanted to join the EEC/Common Market, the Government just did it.
Labour, rightly, said "this isn't right, the public must be consulted." So we held a referendum to see if the public wanted to remain in the EEC.
By referendum, we said we did. Some people weren't happy, but democracy won through and we remained in the EEC.
40 years later and many people (many of whom who voted the first time) have changed their minds. We demanded to be consulted again and were for many years ignored. Eventually we hold another consultation ia referendum and it shows, yeah, we have changed our minds. Being in the EEC has changed, to the point it's not even called the EEC anymore. So by rights, we must therefore leave the EU.
If we change our minds again, we can hold another consultation to see if we want to rejoin the EU. It's fair, it's democratic, it's respecting the electorate. What went wrong?