Dear Marion,
When I awoke this morning, it was obvious to me that on behalf
of my family, I owe an apology for our misrepresentation of Margot
with respect to "die grosse Linie." I heard this mantra often
enough to have no reason to doubt my memory; but I know my parents
well enough to understand that they would seize on a word or phrase
sometimes even out of context, if it seemed significant to them,
and use it as a template with which they would then conclusively
characterize a person's opinions or actions far beyond the intended
scope of the original meaning. The phrase "I wouldn't stoop so low." 
about which I recently wrote is a telling example. I assume the
phrase "die grosse Linie" probably was uttered at some time, in
some context or other by Fritz or Margot and that Marga latched
on to these words as a rationale for her being rejected. Surely it
was less humiliating to Marga to indulge in the fantasy of being
rejected for not being Jewish, than to face the reality of being
rejected because she was considered impossible to get along with. 
I think that's very simple and very sad. I also think it's a telling
explanation for much of the controversy about religious affiliations.
Jochen