The reality of it all is that transformations take time, especially when things at Yahoo had been so Scott Thompson'd. Marissa has been rebuilding a sinking ship from the inside out - where most people would've just tried to patch it up as it slowly sank, or sold it off for parts; I think that's what's admirable. I think that's why people defend her. She dared to defy the status quo. She dared to employ the same dedication as founders do day in and day out, and she demonstrated over and over again, the audacity to take risks.
I find it stranger that more people don't defend her. All of us should know that technology companies thrive or die from the inside; it's why startup founders spend such a disproportionate amount of time hiring great people. To anyone who actually bothered to pause and compare Yahoo's culture today to yesterday's, it would be obvious that Marissa's conviction and aptitude is heralding a new era of prosperity; the transformation is apparent - and even if not yet absolute, it is still miraculous.
Remember: people -> product -> profit