The issue I have is not your view, it is your rationale. You cited a very small portion of history which has been relatively peaceful between countries with long histories of ideological and armed conflict on one hand, but then cited one or two attacks over the course decades where people have carried out an attack in one country, then fled to another country within the EU. In both cases, scanty evidence is cited to prove your point. So no, "dichotomy" is not the right word. Sorry. Poorly formed arguments.
Yes, I contend that at some point in the future, there will be armed conflict in Europe. I feel pretty safe contending that considering some might say we're already there between Russia and Ukraine. I'm pretty sure the French didn't want to fight the Germans... most times you don't have a two-sided vote: it only takes one (again, Russia/Ukraine).
In terms of the EU, the freedom of travel between them is akin to our ability to travel within states. I don't see why that's a negative... someone can commit a crime here and drive from RI to Massachusetts in a matter of a half hour or less. Given that these are not non-extradition countries, the only argument then is that they don't share criminal and intelligence information well, but that remains a problem even with further travel restrictions.
Furthermore, citing ease of travel from one place to the next as a primary concern with the EU is pretty silly given that passport and identity fraud amongst terrorist organizations borders on the trivial.
Anyway.