Actually MS was the one to first challenge National Security Letters. Moreover if it was found out that they had left a back door in it would result in the loss of billions of dollars in business, from Europe alone. Whereas Kaspersky very clearly will always have a Russian government/corporate client.
Are you sure Microsoft was? I thought Yahoo did. I can't find the reference now (Google is full of references to Yahoo being the first to disclose an NSL), but I seem to remember something from 2008-2009 era and Microsoft's challenge was in 2012-2013 era if memory serves. Not that this matters much in the grand scheme, but I'd still love to know which company really has that distinction. Links appreciated if you find one!
I suspect you're right, that said Yahoo has lost all respect from me after they've basically turned over everything without question after Mayer became CEO. In all honesty it's very hard to tell because the challenges are secret and sealed for the most part.
Apple only kind of stood up to the feds, they happily handed over the terrorists icloud account and all things associated, they only refused to be compelled to write software knowing full well that the FBI already easily had the capability to break into the iphone. I would say that the government having some sort of restricted access to this data could be useful and important to society IF, and only if, there were better civil liberties protections in place. DHS has way too much power, and we heard from Edward Snowden that our data is often irresponsibly used.