Yes, it's very easy indeed. Doesn't mean if it's easy it's wrong.
With minimal adjustments, which are very cost-efficient, a lot of suffering could have been spared.
Which there was
No one said every market or city square needs to be guarded. You need to look at probabilities (christmas, amount of people, etc.)
Again 100% security doesn't exist, but that doesn't mean you don't have to take any security measures.
And that's your right to think that way.
Possible increase of terror attacks using motorvehicles.
If there's a bird flu, or whatever, you take measures to make sure it doesn't spread. A maybe somewhat ridiculous analogy, but the point still stands.
If intelligence agencies tell you that certain risk is high, you to take measures (least intrusive if possible, which e.g. bollards are in my opinion.)
It's not, it's only for 'big' events and for a limited time. It isn't even terror related, as I said before, it's used to make a car free zone.
Again, it's just a different mentality about security and the (perceived) severity . Doesn't make one opinion more right than any other.