That's not necessarily true. There are a number of things which can allow the "corporate veil" protecting stockholders from personal liability to be pierced, including a stockholder that is also a corporate decision-maker engaging in grossly negligent or reckless acts as a corporate decision-maker that produce the corporate liability.

Incorporation provides a shield against personal liability, but it is not an absolute, unconditional shield, especially for stockholders who are also decision-makers in the corporation.