A big difference is that Eich is a well-respected contributor to his organization who independently has an unpopular political viewpoint, and his actions only became notable in the context of Mozilla. Whereas Rice is known generally for her actions, has not been involved in creating Dropbox, and was most likely hired precisely for the skills that people despise.

But I also think this backlash comes from people being reminded about the fundamental reality of Dropbox. It's always been a centralized technology with a controller that's free to do whatever it pleases with your data, either for their own gain or simply out of expediency - any sane hacker should have been recommending avoiding Dropbox and its ilk this whole time. Appointing someone who's directly associated with facilitating and justifying hostile acts reminds everyone of this inconvenient truth, which makes those in denial uncomfortable.