Right, "biasing your talent pool" doesn't mean that everyone in that talent pool sucks. There are certainly some very talented C#/.NET devs.
The problem is that when you go to hire, you have very little information about just how badass a prospective dev is, unless you've worked with them before. So if you take a random dev out of the C# pool, chances are he'll be worse than a random dev in the Python pool.
http://www.paulgraham.com/pypar.html