This statement is false as a blanket. I worked at MS in 2010, and I had vim and git installed on my machine. What they didn't want me to do was to install (or look at!) the source code.

The amount of FUD from rank-and-file employees was shocking though. Based on ignorance, but they just weren't part of the GPL world, and didn't care to understand it deeply. So I don't doubt that you may have asked someone and been told "Oh god, don't even look at that stuff". But it wasn't any kind of company wide policy.

I did end up talking to folks that were trying to make such a company wide policy, but even then what they were pushing for was some kind of GPL registry, where if you installed any open source software, you had to register it with the powers that be. I don't think that went anywhere though.