A counter-argument I've read to the dark forest theory is that:

* spectroscopic analysis can show that our atmosphere is oxygen-rich, and this can be detected from a range of many light-years away * oxygen-rich atmospheres probably indicate life * we've had an oxygen-rich atmosphere for hundreds of millions of years

So, yes, radio wave emissions have only been going on for 100 years, but we've looked like a life-bearing planet for 100s of millions of years and nobody's taken a successful extinction shot at us that we know of.