Thompson vs. North American Stainless, LP is the latest ruling to send labor lawyers spinning. This US Supreme Court ruling expanded Title VII protections against retaliation to cover third party employees. In Thompson lower courts had ruled that the employer had retaliated against the fiance of a terminated employee who had brought legal action against them. The employer's defense was that Title VII didn't cover third parties. That the Court ruled for the Plaintiff has caused a new selling opportunity for labor law seminars, as law firms want to teach all of us in business how to protect ourselves from third party retaliation claims.
This is much hysteria about nothing for a couple of reasons. First Title VII already protects against "affiliative discrimination" i.e. protection against retaliation for whites who worked with and/or are friends with a non-white who brought an EEOC charge. Protection of third parties is not a new theory.
Second you can avoid third party retaliation claims with a simple countermeasure: don't retaliate.
One of my first Regional Managers back in my Wal-Martian days taught me that leading people who don't necessarily support you is the highest form of the managerial arts.
If you are in business and you run your operations for efficiency instead of trying to make sure nobody's feelings get hurt you will inevitably be charged with something. Work through the charge and focus on the work. Forget about who did what, trying to exact payback, running off the sympathizers, etc... That only gets you your own version of Thompson.
Getting accused of something at some point in your career is the norm in management; you are probably not doing your job if you don't. Prevailing against charges, self-correcting if you inadvertently do something wrong, and not retaliating are the three elements to keeping you and your workforce focused on business and not conflict: no seminar required.