I think everybody would agree that all is fair in love and war. Any company is free to go after any market, any adversely impacted existing relationships are tactical losses. What's important is how all parties move forwards after the event. You say that Apple is justified to feel indignant. Well maybe so, but the key question here is is Apple's reaction in their own long term interests? Poisoning their brand by releasing crappy software, moving into spaces were they are non-expert, and degrading the experiences of paying customers is at the very least a questionable reaction. Indignation, feeling like you've been backstabbed, retaliation etc. are all words that should not enter the vocabulary of a corporate entity where you want only a highly rational and logical assessment of a situation. I'd argue that Apple's brand would be much stronger (and their products much better) right now if they'd stuck to their core values and brought Google in to power the parts of iOS that they do best (i.e. maps and voice etc.).
Apple either sends users and data to the belly of the beast that decided to complete head-on with them (making Android better, by the way) or figures out how to do this stuff themselves and offers beta products. I would say that Apple doing the latter given Google's aggression makes a lot more sense than Google's aggression in the first place.
Google made a mobile OS because no other company had the software expertise to even remotely challenge Apple. Before Android the OS software from Nokia, Samsung etc. looked like bad jokes compared to iOS. Google created an open source platform that any manufacturer was welcome to use and in doing so blew open a previously monopolised smartphone market. Google's market is selling advertising, it doesn't care if it sells ads off Android phones, or iPhones. The health of the entire internet connected ecosystem is in Google's interest. In what way could you define Google's move to get involved in mobile as "nonsensical aggression"? The aggression at play here is Apple's, voice-search and maps are low hanging fruit for easy monetization, Apple don't want Google anywhere near them and they're willing to screw users to get there.
Google made a mobile OS because no other company had the software expertise to even remotely challenge Apple.
B doesn't follow from A. First off, it's untrue that nobody else had the software expertise to challenge Apple: there's Microsoft, RIM, Palm, plenty others in 2007. Apple had 1% of the market and no monopoly. But let's pretend that none of that is true and that Apple did come to dominate the market. The dependence was mutual, and Apple would have every reason to fear dependence on Google as visa versa. This should have rationally encouraged cooperation. Apple's only alternative for search and web services would have been Microsoft, even more of a direct competitor (then, in 2007), and one to both Apple and Google at that! Undesirable.
Second, Google's handing out bullets to its competitors like candy and is hurting its ability to lock down mobile. In China, Baidu has ripped out core Google services from Android and has replaced it with Baidu services. Amazon has done the same thing for Fire and replaced Google with Bing. If Facebook were to ever build a phone, it wouldn't have to look much farther than Android. And of course Google on iOS isn't long for this world.
Third, the dependence on a single dominant player still exists. Samsung owns the Android space and can hold Google integration hostage for all kinds of goodies. It's pretty much back to square one re: Apple, except Samsung has OS alternatives (including forking Android [hey, who made S Voice?]), where Apple didn't have Google alternatives. HTC is in the dumps and Google is in a tough spot with privileging Motorola, its new baby, for fear of angering aforementioned Samsung.
So no, in short, it's not clear at all to me that this was a rational move.
