If she indeed was about to bring down "our" world of national and ethnic purity and walling itself off in paranoia, then I'm all for this, such abomination should be brought down.
Strawman.
Having strong feelings about limiting the influx of the outside population is one thing. That, however, are pretty much the same arguments, sometimes word by word, used by generations of antisemites brainwashing the people about how Jews are destroying European civilization, or by defenders of the Apartheid and Jim Crow. Sure, you can point out differences between modern refugee crisis and those developments, but the rhetoric remains the same and it never ended well.
If you think ethnic tensions will decrease rather than increase if mass immigration continues, I don't know what to tell you. Natives will increasingly start doing what minorities had been doing all along: think about their own group's interests when voting, and act accordingly outside the voting booth. Tensions will increase and everyone, natives and minorities alike, will be worse off.
Also, the argument about people stopping to try to get over if there would be no NGO rescuers does not hold. We're not talking about the people sitting comfortably on their asses who just thought "hey, I think it may be cooler in Europe!". We're talking about thousands fleeing wars, hunger and unimaginable poverty and that's enough to determine them to risk their lives by crossing over.
I am not trivializing the bad conditions in Africa and the Middle East at all, and I don't blame them for trying to come here. It's just not in our interest to allow them to, and we should act according to our interests.
But do you honestly think
the same number of people would embark on an arduous and dangerous boat trip to Europe if a) they knew there were no NGOs just outside North African countries' territorial waters to pick them up, b) they would never receive asylum in Europe and c) they would actually be deported back immediately rather than being able to successfully stay under the radar illegally and stick around indefinitely? I definitely don't think so. And I definitely think it would save lives. Lots of them, cumulatively, because the earlier we stop it, the earlier we end the massacre on the Mediterranean. But yes, my first concern is to safeguard our countries and if we don't end illegal immigration from Africa, 2015 will be peanuts compared to the influx we can expect this century and we will all be worse off.