You sigh too quickly. The CDs said "Sony BMG." The merger with BMG was in March of 2004 and the rootkit was in 2005. The reason you associate it with Sony corporate and not Bertelsmann (of Bertelsmann Music Group) is because reporters are lazy and shorten the name of the company to just Sony. Maybe Germans were boycotting magazines because that was the part of the name familiar to them. I don't recall that.
Its fair for you to say you're not interested. However, if you're going to try to boycott a company to punish them for their behavior, being aware of exactly who is responsible is a good place to start.
Bertelsmann was just as aggressive with music protection. They had to issue replacement CDs that had anti-rip software to annoyed customers in 2001 for instance. The executive in charge at the time of the fiasco came over to Sony BMG from Bertelsmann.
I worked closely with some of the people involved in it at Sony BMG. One lesson I took away from it all was that even though it was a 50-50 merger, Sony had way more name recognition and therefore more on the line. As you said, they benefit from the goodwill disproportionately and they also took the brunt of the PR damage.