I don't have the evidence to support this, but my educated guess is that a proportion of it is driven by the fact that it was a Pakistani (and presumably Muslim) girl.
The meme pool for Pakistan and Muslims in general is driven by the terrorism / fear narrative; masking one's prejudice and engage in a self-satisfactory public bashing is easy when we also have a competing meme (Microsoft as borg) that can be used to mask the ugly aspects of it.
The other alternative (that people really do hate Microsoft so much that they would make these comments about a dead child) is so childish that I can't bring myself to believe it. It would be morally equivalent to.. well, cheering for people dying without health care. IE: A small group of people so wrapped in a narrative that they can't bring themselves to see how abhorrent their beliefs have become to the majority around them. Are those people us?