Recently I found about two new programming languages(Vala and google's GO) which don't support method or function overloading and intend on not supporting them in the future ever! The creators of these languages say that overloading is evil and should not be used!(in system programming?)

I was told that the creators of Go Language even say that classes are evil as well and goo doesn't support that!

My question is:

Are they really that bad that the new languages are omitting them? Or Is there a specific field of usage for that languages which makes them evil? What could be the disadvantage of using such facilities at all?