It's not clear whether he's saying that threads are bad in Ruby, which is true because of the GIL, or that threads are bad in general, which is just unfounded bashing.
i'm always surprised to hear things like this. it's certainly not unfounded - it's just so obvious and universally accepted that it doesn't require explanation - one would think.
And the concurrency primitives and frameworks in languages like Java and C# are so easy to use there's a whole generation of us who think that threading is the easy way to do concurrency.