I do think the banned comment was the tired, tiresome kind of thing that people who feel passionately seem to find a way to shoehorn into discussions where they are off topic or add nothing substantive. And I think the comment they replied to was as well.
I don't really see much difference, other than the nature of the opinion. Yes the banned poster did address their parent specifically, but... really the parent put out their opinion about a bunch of things, if that is substantive then it should invite questions or disagreements so addressing them on the topic of their opinions is appropriate, surely.
No disagreement there, the glib angry stuff people insert into a conversation tend to flatten all reasonable conversation into vitriolic bursts of outrage or anger.
The EU is not without a great many issues, notably the weakness is the central banking mechanisms of the EU/Euro - and the Euro in inseparable from the EU, and tbh, kinda endemic of the issues with the EU. It's an almost country, its missing the accountability of a full country, but still has some sovereign powers. I think the flaws in the EU are fixable, but not without making it look more like a democratic supranational government.
However, for all of the EU's flaws - the UK is hurting now, largely because of Brexit - who knows, in 50 years it may turn out for the best. But I honestly suspect not - only time will tell.