Why nationalism is on the rise in Europe

The popularity of nationalists in Europe is something that has been discussed for years now. But how is it possible for the nationalists to become so popular?
I will give my own opinion about this topic, and I hope this could lead to a small debate about this topic.

There is no reason to believe that the nationalists are using any other weapons than debating the topic of refugees in ways that the other parties don't dare to.
But how did the nationalists get the "refugee weapon"?

A big part of the new nationalists are the ones who used to be leftists but started to feel that the policy of the leftist parties in the matter of refugees simply didn't represent them. When looking for a new political home, they found shelter under the wings of the nationalists. Besides the leftists many other political parties of the political correct establishment has assisted the leftists in creating this frustration. As an example a non leftist politician that was promoting a political correct debate towards immigrants is Angela Merkel.

Characteristic photo of German nationalists giving a red card to Angela Merkel.

To a large extend the leftist parties denied to see the truth in some of the topics that they found difficult to talk about, or simply because of ideological fundamentalism didn't wish to see.
I personally believe that many people don't want to hear sentences such as "let's expel them all" but just hoped that this topic could be debated by all politicians.
But in the debate if one dared to question if there is a problem they were labelled as fascists.

For me it is very crucial in a debate that all topics can be discussed, and if a large part of the population believes that there is something to be concerned about because of the refugees then there is a topic that needs to be discussed in a constructive way. Even if you believe that there is no problem, you have duty to debate the topic.
Discussing some issues related to refugees doesn't mean that there is hatred towards the refugees.
Not allowing a free speech and not allowing some topics was done in Iraq of Saddam Hussein, the third Reich of Adolf Hitler, Soviet Union of Stalin and in east Germany of Erich Honecker.

Denying and refusing topics is just not the way that democratic societies are working. Denying topics and labeling people for having opinions is something that reminds me of something else. Let me use a photo to define what it reminds me to.

So how would a healthy democratic society be able to disarm the upcoming nationalists?

First and foremost by letting everyone speak about what they want and what they are concerned about! If their concerns are false and their opinions wrong, then let the debate prove that.

If the population of the country that hosts refugees believes that raping is a problem that is growing ever since the arrival of refugees, then the solution is not to deny things or pointing to other statistics than the skeptics. Instead starting to solve the issue is the democratic approach in case there is something to solve.

At the end of the day many refugees are coming from countries where if girls dress up as they do in the west, it means that they are available for sex.
So of course the hosting country needs to explain the cultural rules of the host nation and to educate about how this society is working.
How can you expect people to understand something that they were never told about?

This is something that can be a part of the debate if the debate will be more open in the future.

My opinion is that if all parties would dare to debate this topic without fear, then the nationalists will be unarmed within a few years.

But that is just my opinion, how do you see this topic?