Is it permissible for us to demolish a nightclub if no one knows of our action, knowing that its owner will lose his money, and is this considered one of the ways of enjoining good and forbidding evil?

Enjoining good and forbidding evil should be done according to one's capacity. This includes reporting the evil to those in authority to remove it, or addressing the owner to dissuade them from investing in the evil. However, destroying the nightclub is not permissible due to the resulting harms, such as damaging property and implicating innocent people. Furthermore, the owners of the nightclub might not abandon their wrongdoing.