First off, only someone completely unfamiliar with the political landscape in the U.S. would suggest that the country is "divided 50/50 on politics." That could not be farther from the truth.
Secondly, I love how when people claim that CEOs/actors/whoever should "stay out of politics" that they don't even realize the irony in a statement like that. What gives YOU the right to tell people what to do, or what certain people should do? Here's one for you:
I think YOU should stay out of commenting on politics. How is that?
Tim Cook, you, I, and everyone else has as much right (and often responsibility) to comment on whatever situation is at hand. This concept that keyboard warriors get to decide who should shut up and who shouldn't is so absurdly narcissistic that it is practically bewildering (it would be, but I'm so used to it that it's gone from angering to bewildering to amusing for the most part these days).
Finally, Tim Cook is an important voice on this issue because he is the CEO of one of the most important and most valuable companies in the world. If the CEO of Apple, of all people, shouldn't be commenting on a bill that has to do with EMPLOYMENT, then who the frack should be?!
Then you should be fine if Tim Cook took a stance on a political issue that you don't like, no matter if you own stock or not.