The biggest gripe I have with that attitude is that it destroys the FOSS, Apple, and Linux movements. People that are new to the IT world don't have years of backgrounds with projects and are going to be picking up on the attitudes of the people already there as well as struggling through technical problems. If they're instantly exposed to a very negative attitude (towards themselves, others, or really anything) it's going to be a huge turnoff to whatever project it is. The negative/hateful attitude that a lot of people have towards Microsoft actively hurts the same cause that they're trying to help.
The other part of that is that with any social interaction someone that is constantly putting something down is perceived (usually rightfully so) as being insecure about their own inadequacies. I don't know about others, but Linux and Apple have both matured to the point that I'm quite comfortable quietly evangelizing and building others up, regardless of the OS choice.
It's time to relax guys, we finally have an atmosphere with the freedom to pick your own OS and to be happy with it. This is a GOOD time to be a nerd, and a fantastic time to share that passion and excitement with people from whatever background.
Besides, if there's someone to demonize, it's the people that don't take the time to secure their boxes. Those come from all distros/OS's and I'll gladly pass the pitchfork around for them!