Not necessarily.  The Minnesota Supreme Court addressed this question in Hedglin v. City of Willmar.  582 N.W.2d 897 (Minn. 1998).  The Minnesota Whistleblower Act protects employees from retaliation when they report “a violation or suspected violation of any federal or state law or rule adopted pursuant to law.”  In Hedglin, the court held that an employee’s report that some firefighters were showing up to fire calls while drunk was not protected activity because, while reprehensible, no statute or rule prohibited that conduct.
On the other hand, the Hedglin court held that employees did engage in protected activity under the Whistleblower Act when they reported that other firefighters were falsifying roll call sheets and driving fire trucks while drunk.  The court concluded that those reports were protected because they involved violations of state laws prohibiting the theft of public funds and the operation of motor vehicles while under the influence of alcohol.
Takeaway for Employers:  Just because an employee reports conduct that is immoral or reprehensible does not necessarily mean that the employee has engaged in protected activity under the Minnesota Whistleblower Act.