The stock value is a relevant metric to assess the credit worthiness of a company. Large profitable companies run a lot of their business on loans. In fact in order to achieve high profit margins it is encouraged as the return on investment is a margin of equity.
If you invest 100 dollar and you do business giving you back 110 dollar, you have a 10% margin.
If you invest 200 dollar, of which 100 are your equity and 100 are borrowed and you get back 220 dollars and pay 5% interest on the borrowed money, you have 15 dollars on your 100 dollar equity. Now your margin is 15%.
So many companies run a significant portion of their business on borrowed money. You hurt their ability to borrow, you hurt their business directly. And this can create a downward spiral. Loans get more expensive to margin gets smaller so more people divest so loans get more expensive...