I can't reproduce this. Unless you mean they should be able to resize not only columns, but the object itself. That's not possible. Users will be able to resize columns in an object, but can't resize the object when you disable Move/Size Sheet Objects.
If I enable "Move/Size Sheet Objects", it allows the columns to be resized, which is desirable behaviour for us, but it also allows the object to be moved and resized, which is extremely undesirable.
If I disable "Move/Size Sheet Objects", the objects are locked which is good, but the data column widths is also locked which is undesirable, as some data which is too large for the current column appears as hashes.
From what you say, with "Move/Size Sheet Objects" disabled, column resizing should still be allowed. Is there another setting somewhere I'm missing, something on the server for instance?