What Steve did in one campaign isn't relevant. He didn't put up 'doodles' on every annual holiday.
What's so special about MLK day 2015? Did Apple do anything for it last year? Year before that? How about the one before that? How about on any MLK day in the last 10 years? No, they didn't. They did this when Mandela died and I didn't think it particularly appropriate then, either. Apple doesn't really have anything to do with race.
One thing Apple does have a lot to do with is education. Their products support children and adults through their learning, and Apple's products are particularly popular in that area. They have lots of unique offerings which can help people learn. For a long time, Apple was the only computer manufacturer which offered student discounts where they operated. iTunes U is fantastic.
Let's imagine Apple started working closely, publicly with UNICEF to support children's education initiatives around the world. That's entirely appropriate, because education is relevant to what they do. Now let's say they had a page congratulating Malala Yousafzai on her Nobel prize and pointing to women's education initiatives which they support and so on. That would all be entirely appropriate and you wouldn't hear a cynical peep from me.
Martin Luther King in this instance is just a random hero. He's a guy whose message of equal civil liberties can't really be disagreed with. He doesn't particularly fit Apple in any way, shape or form. He doesn't belong here. It's not appropriate.
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You couldn't be more wrong. This isn't about MLK at all. That's kind of the point. He has nothing to do with Apple. Race relations is not an issue which involves Apple at all. Civil rights is not an issue involves Apple at all.
Apple's website is a professional corporate site, not a blog. Google can get away with random stuff like this because you don't expect professionalism from them. You do from Apple, and it's a shame that they're transitioning in to one of these clueless companies who feel the need to chime in on every event or holiday happening in society.