YOU SAID:
they couldn't deal with that sort of thing
INTO JAPANESE
彼らはそんなことを扱うことができなかった
BACK INTO ENGLISH
They couldn't handle such a thing.
INTO JAPANESE
彼らはそんなことは扱えなかった。
BACK INTO ENGLISH
They couldn't handle such a thing.
That didn't even make that much sense in English.