> Google is making the (completely wrong) assumption that those people cannot type google.co.jp instead of google.com and make their own choices.
You're making the completely unsupported assumption that the average internet user understands domain names. Like patio11 suggested, if a user from a Japanese IP is accessing google.com, it's likely that this address was pre-configured in some way: the search bar was set up like that, or the company sysadmin set up the home page like that. But even if the user manually typed "google.com", if they're in Japan it's still (way) more likely that they wanted a Japanese version rather than the English one.
Come on, most users outside the US are perfectly used to a plethora of international TLD's. It's something they are quite familiar with.
Also, they either use the English version of the OS and browser, or the one in their language, and both come with the default correct preferred language settings.
The same goes for company systems. You don't give someone who can't handle English an English language system, and the idea of setting up a system in language X but pre-configuring that in some what that English becomes the preferred browser language is a really odd edge case.
Even if such scenarios are more common, it still doesn't excuse telling people that make explicit choices to go fuck themselves, especially in multi-lingual countries where such explicit choices are common.
Japan may be relatively homogenous, but most countries in Europe are either formally multilingual or have large immigrant populations. Many thousands of people are regularly being confronted with misplaced assumptions about their preferred language.
You can't assume language from geo-IP databases, it is the most unreliable and inappropriate method imaginable, and you are 100% sure to regularly piss people off.
You're making the completely unsupported assumption that the average internet user understands domain names. Like patio11 suggested, if a user from a Japanese IP is accessing google.com, it's likely that this address was pre-configured in some way: the search bar was set up like that, or the company sysadmin set up the home page like that. But even if the user manually typed "google.com", if they're in Japan it's still (way) more likely that they wanted a Japanese version rather than the English one.