Why is Merkel so dead-set on continuing to allow unlimited immigration?

Edited from a comment on another blog:

Most people seem to think that when the Berlin Wall came down, and the Soviets appeared to dissolve the Soviet Union, that suddenly millions of die-hard communists magically stopped being communists. They didn't.  Instead they stayed in the same jobs as always and continued doing what they had always done before.

Some members of the East German military were given positions in NATO, because everyone wanted to believe there was no more communism...except that those people were still communists. Just because they started wearing new uniforms and pretended to be everyones friend didn't make it so.

The specters/незамеченным/Unsichtbaren of the East Bloc/Soviet Union past will eventually be paying a visit, and it won't be a pleasant visit.

About five years ago I read a very long profile of Merkel in Der Spiegel, and the reporter was very candid about Merkel's communist background.  But after the fall of the Wall, suddenly every reporter and pol in the west has forgotten that communism ever existed.