Network support has been an OS feature since before Microsoft even existed.

http://en.wikipedia.org/wiki/Ethernet

http://en.wikipedia.org/wiki/Microsoft

Yes, there are people that probably would have preferred Peter Tattam's company to be bought by MS. (It was shareware, see thread here: https://news.ycombinator.com/item?id=2282875). But it definitely wasn't an obligation.

Very few would argue that an OS has to have a browser to be functional. Just like very few would argue that all networking should be done in a user space process not part of the operating system.

An OS doesn't have to have a file browser either, yet no one cried antitrust when Windows 95 bundled Windows Explorer instead of forcing people to buy Norton Commander.

This whole argument is kind of silly anyways since it's leaving out intent, which is a very important contextual part of evaluating the action of a person or entity. Seeing emails showing MS trying to deliberately get web developers hooked on a "more standards-compliant" IE and then locking those same devs in is a much different thing than MS honestly wanting people to have a decent default software base to go with Windows, even if both strategies end up in practice with "IE 4 preinstalled".