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 moved from commercial .NET coding to startup-land a few years ago, and there's definitely a learning curve. I had to ditch Windows on my personal PC and start using Linux at home to really get the hang of it. YMMV.