Delete - Model - Load Individual, choose the "All Load Sets" option, hit OK, choose the nodes, hit OK, don't pick any elements, just hit OK, they'll be gone. You can then delete the nodes.
Femap will not allow you to delete nodes if there are elements using those nodes. You can use Delete -> Model -> Mesh to delete elements and their nodes, but only those nodes which are not attached to any remaining elements will be deleted. Your initial question suggested that you had "orphan" nodes (unconnected to elements) and the nodes refused to delete only because of the loads on the nodes. But your 2nd post indicates the nodes are also connected to elements. Femap will never allow you to select just nodes and delete those nodes if used by elements. This is not a bug, it is deliberate design. Similarly, a material cannot be deleted if used by a property; a property cannot be deleted if used by any element - the "parent(s)" must be deleted before the "child" can be deleted.
Occasionally (fairly rarely) entities refuse to delete even if they have no parents - this can be sorted using File -> Rebuild, then delete.