What is one defect that would condemn a flexible wire sling?

A flexible wire sling is critical for safely lifting and moving loads, and the integrity of its construction is paramount. Broken wires represent a significant safety hazard, as they indicate that the working strength of the sling has been compromised. The loss of even a single wire can reduce the sling's load-bearing capacity, increasing the risk of failure during use.

In the context of the other options, while surface rust may affect the sling's aesthetics and could eventually lead to deterioration if left unaddressed, it does not immediately render the sling unusable unless it has progressed to a point where it significantly weakens the wire. Minor bending, while undesirable, does not condemn the sling unless it affects the overall structure and function in a critical way. Excessive length does not affect the load-bearing capacity directly but can introduce handling difficulties or challenges in stability. Ultimately, any instance of broken wires constitutes a clear and immediate danger, requiring the sling to be taken out of service.