I used to be of the sweet, philosophical and benign alien school, but arguments like the one you've outlined have made me suspend judgement. True, it is comforting to think that ETIs will be curious, and as eager to meet and communicate with other intelligences as we are, but at the same time we must realize that the OTHER GUYS are totally unknown, and if they're bad news and stronger than you are then you've given away the farm and there is no going back. And they will know this too, perhaps even from bitter experience. Even a peaceful and humane species may think twice about giving away its homeworld, or even its existence away. And if it does so, the only way it can guarantee its survival is by a preemptive strike (providing it is successful!). Much more thought needs to be given to this before we embark on active programs. Maybe that's why the ether is so quiet.