Earlier quoted context omitted.
Their users don't need to be allowed to freely evaluate the source, period. When you write software, you control its distribution. What the users are free to do, however, is use an operating system/stack that they CAN evaluate the source of. If linux or any other open source alternative was a better actual product, it would find its way to the top of the market. In fact, it already has, on the server... by far. But l…
The sentiment of "the better product will win" is understandable, but wrong as you present it. Microsoft managed to gain a monopoly (legally or illegally - doesn't matter) and has used it to illegally keep others out, and network effects now (and for the past 20 years) have been that "goodness" measure - technical mediocrity had been sufficient (although recently they have been doing a lot of excellent technical work…
If there is a Linux solution that in every way exceeds a Microsoft Solution from a technical and price standpoint, you still need to weigh in the transition costs, employee costs, and the long term effect of changing. It's not always as simple as "X is better than Microsoft's Y, people will use it." There are far more things that get considered, and you can get tied down pretty heavily when your entire workflow and operations rely on a single product or vendor.
The longer you've been using a product, the harder it is to get away from it. It's not that Linux isn't good or making a lot of cool progress in all realms, it's that Microsoft does "good enough" and the transition isn't seamless enough for many use cases.