Is that tweet really "extremely negative" towards Linux? All he says is that he doesn't want to abandon Windows but instead push back on changes to it he doesn't like; he doesn't make any judgements about Linux. The reality is there are many barriers to Linux replacing Windows as a desktop platform for users today so it's not surprising that someone who runs a business that depends on users doesn't want to push for a huge switch to Linux if it's not necessary. If a company not wanting to act outside it's interests makes it Linux's "biggest enemy" then it will be a very long time before it succeeds as the major desktop platform.