First, let me tell you that the biggest majority is not against migration. Hasn't been this way for idk, 50 years? Germany has been a net immigration country for some decades now. There is some fear mongering along rightwings and racists that have become more mainstream because of the sheer masses and the bad organisation last year (we Germans like planned, organized things). Words and statements, that were a no-go and career-ending 5 years ago, will now just hit the sweetspot of publicity and outcry. So the pseudo-rightwing, quasi-fascist AfD has about 12% in recent representive polls.

I don't think it's a racial fear in itself but more because of the last 20 years of islamic terror I guess (and the fear of letting your guard down, as Germany wasn't target of a big terror attack). People become xenophobic because they don't know what will happen and if the culture will change like the IS and some islamic radical propagate it. Religion isn't a very big part of Germany anymore, most people aren't everyday-religious. An alien (or not so alien, we have a very big Turkish minority) religion that defines the everyday life of the immigrants seems a big change to some of them. As well as the role of women, which estranges Germans as well.

That being said, I guess the biggest issue right now is the high number for most of those that feel like they should "protest" by voting for the AfD. As I said, the Nazi-core just plays their cards pretty well.

Hope that helps understanding. Canada always seems like a big role model for immigration but I actually don't know how many refugees you took in this crisis (not a critical statement, just a fact I noticed right now).