According to the Public Relations Society of America, “Public relations is a strategic communication process that builds mutually beneficial relationships between organizations and their publics.” Notice the emphasis on building mutually beneficial relationships. The PR Rep who posed as a reporter was clearly not trying to improve relationships between the union and the Walmart corporation. Instead, she was gathering information that would support Walmart in future negotiations.
As the representative of your organization this kind of public relations crisis can be avoided if you just remember the Golden Rule. Long term, that’s always the best guideline in business.