I find that the constant, hateful refugee-bashing is sickening and unworthy of a democratic nation.
First of all, 'refugees' who come to commit acts of terrorism are not refugees by definition. They are infiltrated immigrants. They never were refugees to begin with. People fleeing war do not deserve to be persecuted because of terrorists.
The idea that Germany is being punished for being too open and tolerant is a twisted one.
Take for instance France, a country that is much much less welcoming toward refugees. It has suffered terrorist attacks too. In fact, it's been hit more badly than Germany. Note that some of the attacks were carried out by estranged Belgian/French nationals. Home-grown terrorists. It's not even foreign fighters coming from some war zone far away.
By the way, the US has been hit by Isis too (eg Orlando nightclub shooting). Do they take a lot of Syrian refugees in the US ? They don't.
On the other hand, more than one million Syrian have fled to Lebanon and now make up 20%+ of the population, which is a huge burden for a small, fragile country. They don't make the headlines but they sure have enough problems.
In short, for those who are too lazy to read or think: there is no correlation between refugees and terrorism. (Or put it differently: intolerance does not pay and doesn't make you safer. There is no reward for racism).
Terrorists come and go, either through official channels and border crossings, or stealthily (when they are already known and flagged as a security risks). They always have traveled in and out. Current streams of refugees do not change the fact. Reinstating national borders would not help either. Achieving secure borders is an awfully expensive endeavor and would amount to building a new Iron curtain (and a radically different society).
However, one thing that could reasonably be argued is that the large influx of refugees makes it difficult/impossible to vet each candidate for possible security risks. That wouldn't necessarily help spot and defeat terrorists though. Attackers were already known to the authorities weren't they.
Bottom line, what Isis is trying to do is foster fear and hatred and destroy social consensus.
I have to say they are doing a good job. Racists and citizens with fascistic leanings are now feeling more confident and getting bolder by the day (racists are always looking for excuses to justify their hatred). Sadly they are just playing Isis' game. Extremists of either side are pursuing the same aim by different means. The aim is to destroy our societies and our democratic values.
Terrorism is not a new phenomenon. We have experienced it over the past decades but today people are hysteric and willing to relinquish all their freedoms and live in a police state for what ? For an illusion of security. Why do we allow this to happen ? Why ?
If you no longer believe in your own values then yes you have a problem. And the terrorists have won. When you stoop to their level, they win too.
When you stand up for your rights, for freedom, for democracy, for tolerance and justice, they lose and you win.
It's up to you.
But there is no easy path. There is a painful path and there is a worse one.