Nike's embrace of Colin Kaepernick has been wildly successful for the company, even though it runs afoul of standard branding practice. While most brands target specific demographics by age, sex, and even ethnicity, they've shied away from political affiliation.
However, maintaining a politically agnostic brand image may not be possible in an increasingly divided society. Whether they like it or not, brands may be forced to "take sides" in today's controversies, for three reasons.
First, brands are all about tying your products to specific emotions, and at this point in history, politics and social change are generating such massive amounts of emotion that they're drowning out other emotions.
Second, the internet has made corporate donations more visible. A CEO can no longer give to a particular cause, party, or candidate without angering half of the population. And because tempers are high, giving to both sides only tends to anger both sides.
Finally, the penalties for backing the "wrong" cause are higher. Boycotts are easier to launch. Employees have new ways to organize and express opinions, not just among themselves but to the public.
Microsoft and Google, for example, have both heard their employees complain about and revolt against their company's product being used to help ICE imprison children and oppressive governments arrest dissidents, respectively.
Nike, of course, has always been an innovator in brand development, so it's not surprising that it would figure out that it would be in its best interests to drive the process of "taking sides" rather than simply react to our society's increased divisiveness.
By associating its brand with Kaepernick and the Black Lives Matter movement, Nike increased its brand's attractiveness to a rapidly-growing, young, urban, hip, ethnically-diverse, demographic--the very people most likely to buy expensive athletic footgear.
At the same time, Nike also intentionally cut loose a declining, older, rural, squarer and whiter demographic that was never a big part of their target customer base anyway. A different brand might find the opposite smarter (think Hobby Lobby).
In short, Nike's successful campaign is evidence that because America is sorting itself into two mutually-exclusive, mutually-antagonistic demographics, brands that want to become part of their customers' identities may need to decide which demographic is most valuable.
The two opposing demographics in the United States are not without historical parallel.
In the Sixth Century CE, the Byzantine empire had also sorted itself into two opposing factions: Green and Blue, so identified by the colors of the clothes that they wore during sporting events. The factions weren't just about sports, though.
In every city of the empire, the Greens rooted for Green charioteers, patronized Green markets, supported Green politicians, and believed a "Green" interpretation of Christianity. The Blues did likewise. Mutual detestation hung heavy.
In 532 CE, a fight erupted at the Hippodrome and rapidly metastasized into a multi-day riot, with extensive looting and burning. The government was forced to suppress the riots by setting soldiers on the population, resulting in 30,000 deaths.
So while, from a branding perspective, you'll probably need to "take sides" (because you'll be buttonholed into one side regardless), You should also be aware that, if history is any guide, the toxic combination of sports, politics, and religion isn't likely to end well.