Is the anti windows/.NET bias really that common? I have been a .NET dev for 6 years because that was my job. But I don`t believe that makes me useless on any other stack. In fact lately I desire to work on something that feels exciting and fresh again but sometimes I feel like .NET devs are looked down upon and it`s not so easy to land a job or contract outside .Net land.
I think it's less common now than it used to be but back in their heyday Java devs looked down hard on .NET devs. I think it's because MS visual IDEs, going all the way back to vb6, made a lot of people think they were professional developers just because they could create a basic crud program with a functional GUI very easily. This ended up promoting a huge amount of unusually bad code/coders to production environments and with that the bad rap .NET devs get to this day. The perception is that developers outside of the MS ecosystem usually have to be a little bit more erudite in the way they went about learning their programming language of choice.