Stallman wouldn't install Windows on his computer or one set up specifically
for him, but he wouldn't refuse to use a Windows machine (because it runs
Windows) for limited use. RMS: "However, if I am visiting somewhere and the
machines available nearby happen to contain non-free software, through no
doing of mine, I don't refuse to touch them. I will use them briefly for
tasks such as browsing. This limited usage doesn't give my assent to the
software's license, or make me responsible its being present in the
computer[...]"
It seems like you are thinking about Stallman refusing to install Windows on
his computer, and I am thinking about Stallman not refusing to limited use of
someone else's [public] computer that contains Windows or other proprietary
software?
I am just deducing that he wouldn't refuse to use a Windows computer, just
like he would not refuse to use a GNU/Linux distro like Fedora or Ubuntu that
contains some non-free software, as long as it is limited usage, and he
didn't set it up. "That reasoning is based on the fact that I was not
responsible for setting up those machines, or for how that was done. By
contrast, if I were to ask or lead someone to set up a computer for me to
use, that would make me ethically responsible for its software load. In such
a case I insist on free software, just as if the machine were mine."
