As an IT auditor myself this behavior is unprofessional and unethical. My job when doing internal audits or an external audit for a client is to help them improve, and not to harm the business I am auditing.
The business would certainly want to know about serious risks or deficient processes that endanger the business. As an example, by reporting to management that privileged access control is weak, or software change management is is inadequate through tangible evidence gathered from testing, I am doing a valuable favor to my client.
I am bound by my profession' guidelines regarding Evidence and per the guidelines, in the case I am not able to obtain sufficient evidence for the basis of my opinion due to non cooperation of the auditee, I must attempt to obtain evidence by other means if possible and disclose to management. Management should be reasonable to understand that by deliberately hindering my work, I will be digging deeper for the information I requested.
It is a non - disputable fact that the business wants to survive. My goal is to assist them by bringing to light obstacles that hinder the business meeting their ultimate goal of survival. Non cooperation only hurts the management of the business - an irrational decision.