It's Because That's Often Exactly What They Are...

“People are being treated like weapons,” said Van Leeuwen (medical emergency manager with Médecins Sans Frontières), who recently returned from a week-long assessment with local groups including the Ocalenie Foundation and Grupa Granica.

“It’s hard to believe this kind of crisis is unfolding in the EU.”

No, it really isn't. In fact, it was inevitable, when you push Open Borders on an unwilling population. 

Sooner or later, they realise that the people you are inflicting on them, and who are not welcome, are indeed weapons to be resisted. 

At least eight people have died as thousands of migrants, mostly from Iraq, Iran and Syria, have tried to cross from Belarus in recent weeks but found themselves trapped in a densely wooded border zone with no food or shelter from subzero temperatures. All non-residents including journalists, aid workers and foreign observers are barred under a state of emergency declared by Warsaw from entering a 3km-deep (1.9-mile) strip along the border. This week Poland sent 2,500 more troops to the area, bringing to 10,000 the number of soldiers helping border guards prevent attempted crossings, after several incidents in which groups of 60 or 70 people tried to tear down a razor-wire border fence.

Who are these people, anyway? 

...many of the migrants also have significant mental health issues after spending sometimes several weeks being shunted back and forth across the border. “These people need shelter, food, water and medical assistance,” she said. “Their lives need protecting, and they need to be treated according to EU and international law. They are not weapons, they are human beings.”

They are an invasion force. 

They don't come with guns and tanks, but with resource-draining ailments and demands that countries forced to be unwilling hosts should change their own culture to better accommodate them.   

And they are not 'refugees' in any meaningful sense of the word. They will happily tell you so, should you ask:

In September Ahmad Dandashi, who fled Syria for Lebanon in 2012 and then spent more than seven years working for the Norwegian Refugee Council helping fellow migrants, paid $1,200 for a return flight from Beirut to Minsk, via Dubai.

“The country was collapsing,” said Dandashi, 29. “The economy was nosediving. There were constant power cuts. It would get worse before it got better. I’d applied for so many jobs elsewhere, for scholarships … But nothing came. I had to leave.”

A friend had made it to Germany via Belarus and Poland in July, he said, and he and a small group of friends decided to try for themselves.

He's not fleeing war or persecution - he's fleeing a country he and his fellow co-religionists have turned into a cesspit. He's fleeing it because do-gooders like Van Leeuwen have made it easier to do so:

Dandashi made it to a processing camp in Eisenhüttenstadt, just across the German border, and filed his application for international protection.

But the 'international protection' he demands comes from the western nations. Not, you'll note, the other Muslim countries.