Google and the NFL are both big private companies that are trying to establish a brand and make a buck. They are not federal agencies or public utilities, though we treat them as some sort of common property. They fire people who are bad for business, even if they're right. They can do that. There are limitations on why they can fire people, but "doing distracting stuff that makes us look bad" is actually a fairly well-established reason, so long as you can show it's not just an excuse.
There are differences. Kaepernick repeated his action even when told it was bad for business; the politics are reversed; Kaepernick had a contract, which means both sides had given up some freedom to operate in exchange for some guarantees; the Google memo is not a whistle-blower case, but it has some elements of that, and some lawyer may try to pry that open; Kaepernick was complaining about something outside his industry.
Yet there is a core similarity. Don't be bad for business, or you will be on the defensive.