This is a fun soundbite, but it's completely arbitrary and meaningless. You could just as easily and accurately come up with something along the lines of "if a union causes its employer financial distress, it is a liability".
> If they cannot afford proper safety equipment then the business is a liability.
And
> If buying safety equipment causes an employer financial distress then it is a liability.
But I think most people would agree with the first statement and disagree with the second.
Except that has been an actual feature of unions. Plenty of unions have agreed on work reduction and other cost abating ways to help a struggling company continue to function in times of distress. Workers plenty well understand that a failed company provides them none of the benefits of the union.