It inevitably leads to a culture clash. Especially when it's uncontrolled and the native population perceives it as a growing threat. A threat to their way of living, to their resources, etc. People have always fought off foreign invasions, but there is no army in this invasion so civilians end up fighting other civilians. These guys aren't mentally ill, they're "protecting" their tribe/pack. It's a very natural instinct, which makes it really impossible to suppress in the long run. It sucks for all people involved but it's bound to happen. In the next economic crisis, when millions of males lose their job, shit will really hit the fan. Something must be done now to alleviate this tension before it spins out of control.