It’s just that doing so would unleash a raft of Equal Opportunity lawsuits.
No equal protection for political beliefs.
Do what many employers do. Come up with a more acceptable reason. Job performance, elimination of the position, downsizing and so forth.
When I worked with a labor union in CA every time there were budget cuts the union leaders would say that any layoffs should be republican members.
In Kansas the boss can fire you just because he is the boss and you are not. No stated reason is needed.
They are willfully ignorant when it benefits themselves. That in of itself is reason enough.
Just claim you lost confidence in their ability, like what’s going on with all the military officers these days.
That will just mean that the Obama voters will be clobbered hard by John Galt