The case involved an employer's refusal to rehire a former employee. An employee who attempted to rally coworkers in support of the former employee was deemed legally protected.
The thing about the National Labor Relations Act is that it protects "concerted activity" and not just you acting on behalf of yourself. So trying to get coworkers to support an intern or a potential hire now falls within the legal protections of the NLRA.
The Board explained what constitutes "concerted activity":
Thus, as the Board has explained, the statutory concept of protected concerted activity has two elements: the employee’s activity must be “concerted,” and it must be “for mutual aid or protection.” E.g., Fresh & Easy Neighborhood Market, Inc., 361 NLRB 151, 152–153 (2014).“[W]hether an employee’s activity is ‘concerted’ depends on the manner in which the employee’s actions may be linked to those of his coworkers.” Id. at 153 (citing, inter alia, NLRB v. City Disposal Systems, 465 U.S. 822, 831 (1984)). The Board has held that concerted activity “encompasses those circumstances where individual employees seek to initiate or to induce or to prepare for group action, as well as individual employees bringing truly group complaints to the attention of management.” Meyers Industries, 281 NLRB 882, 887 (1986) (Meyers II), affd. sub nom. Prill v. NLRB, 835 F.2d 1481 (D.C. Cir. 1987), cert. denied 487 U.S. 1205 (1988). Notably, the “object of inducing group action need not be express,” and an employee’s statement may, in certain contexts, “implicitly elicit support from his fellow employees.” Whittaker Corp., 289 NLRB 933, 933–934 (1988). As the Board stated in Meyers II, “the question of whether an employee has engaged in concerted activity is a factual one based on the totality of the record evidence.” 281 NLRB at 886. “Mutual aid or protection,” in turn, “focuses on the goal of concerted activity; chiefly, whether the employee or employees involved are seeking to ‘improve terms and conditions of employment or otherwise improve their lot as employees.’” Fresh & Easy, supra, 361 NLRB at 153 (emphasis in original) (quoting Eastex, Inc. v. NLRB, 437 U.S. 556, 565 (1978)). Both the “concertedness” and “mutual aid or protection” elements under Section 7 are analyzed under an objective standard, whereby motive for taking the action is not relevant to whether it was concerted, nor is motive relevant to whether it was for “mutual aid or protection.” Id.
The Board further elaborated: "It is well established that “the activity of a single employee in enlisting the support of his fellow employees for their mutual aid and protection is as much ‘concerted activity’ as is ordinary group activity.” Whittaker Corp., supra, 289 NLRB at 933 (1988) (quoting Owens-Corning Fiberglas Corp. v. NLRB, 407 F.2d 1357, 1365 (4th Cir. 1969))."
Bottom line is that you are allowed to speak up about working conditions and to attempt to get coworkers to take action regarding working conditions. You don't have to succeed in rallying coworkers to join you. Advocating on behalf of non-employees such as potential employees and interns is now legally protected.
If an employer retaliates against you for doing so, or for taking any other protected concerted action, then you can file a charge against employer with the NLRB within 6 months from the date of retaliation.