It might sound tactless because it breaks down the illusion of moral superiority that most sides in a political battle believe they have. In general, people don't like being told they may in fact be wrong, they want to believe their side is unique, superior, and the other side is committing crimes against humanity/unborn children/whatever it may be. When a huge proportion of the broader population (not necessarily HN) disagrees, in order to function as a society we need to remove these litmus tests. (The most compelling Rice-specific argument is about internet privacy vs. government surveillance, which goes beyond this - he's speaking of the "personal becoming political" in general)
It's completely relevant to the debate though and not de-railing, when it directly addresses the point of boycotting Dropbox for something political. Our society is becoming more polarized on these issues and (internet) forums of self-selecting ideologies and subgroups contribute to this. Going boycott is one weapon in an arsenal of political expression - now how often should people use it? (The next level of course is street protest, institutionalized ideology, and the extreme is fighting a war over it).
If we used a boycott at every opportunity, at every disagreement, where would we be? Would Christians, Muslims, and atheists ever do business with each other? Would pro-lifers and pro-choicers be able to open their mouths without calling each other baby murderers/misogynists? He's basically saying, draw the line closer to where the overall population is, so society can function without imploding. And we generally go about this on an everyday basis. Geographical self-segregation also tends to help. It's a moral cognitive dissonance, but one that people draw various lines for. My theory is those who have a more logical/black and white and less socially influenced conception (which may be more common in geeks) have a harder time squaring with this cognitive dissonance.