Am I right
that your objection is "The articles on
marxists.org are
wholly unsuitable for inclusion in wikipedia under the titles they
have on that site."
That's right.
I've yet to see anyone disagree with you on
this.
I agree.
That might be a diplomatic way to approach them--just say that
all of their stuff is welcome, if titled "Marxist views on X..."
or similar, and that some information from those articles might
also make its way into the "X..." articles themselves, but not
most of it.