The OP mentions :-
"she said the UK and the other countries had fought to save Europe and it was strange that they'd fought so hard to protect something that we are now leaving."
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' IF' and when we leave the European Union we are NOT leaving Europe. How can we ever leave Europe? Say we are now on the Continent of Asia, Africa, we are a country situated on the Continent of Europe. The repeated mantra 'the UK is leaving Europe' is quite frankly a stupid comment.
What was being fought for in WW 2 was freedom from the tyranny of Hitler and Germany who had occupied countries in Europe, obvious. We knew that we were next on the list and fought not to stay in Europe, how on earth could we leave Europe but to save our skins from Hitler and the Nazi Party invasions. Even Hitler had he won WW2 could not have divided countries from being part of the Europe /European Continent.
The UK joined the EEC in 1973, we had been blocked from joining earlier by France, the European Union was formed in 1993 ( Maasterich Treaty) so we were not fighting to stay in the European Union we voted to leave an Institution formed in it's current form 26 years ago certainly not at the time of WW2.
Everytime I hear a typical comment ' The EU keeps us safe' and some go so far as to say our leaving could create another possible war, put the UK in a perilous position, I think they have lost the plot quite frankly. Why is it the UK being outside of the EU is viewed so differently to other European countries outside of the EU such as Switzerland, Iceland, Monoco, Norway? Are those countries in danger too? Will the EU single out the UK for attack?
The commemoration of the d day landings to be honest reminded me that whilst Europe was not in a political union during WW 2 the UK and other European countries came together to try and beat evil and not only European countries nations such as Australia, India, Canada etc.
If a country is under threat, for example Ukraine which is not in the EU, it will not be only countries in the EU that would do the right thing. Likewise if another European country tried to start a war, whether they be a member of the EU or not I believe countries in or out of the European Union would do the right thing.
I would be greatly concerned if NATO collapsed and I hope the countries in both NATO and the EU are never put into a position where they must decide where their loyalties lie and NATO is diminished but I do think that could become a distinct possibility when listening to some of the comments from ' some' in the EU. That to me is more of a concern than the UK leaving the EU if the sole point of the topic is defence and being put in danger.