Without Channel 1, there is no way of knowing that a "new" player is tuned to 200. The only way to know if they can see your message is to personal message that person. Ask yourself this question: How many times have you come into the AvA and found a new player on the roster in the country that is not enabled?
Okay, here is another example of why channel 1 is a good idea: Recent posts talk about the mentoring of sorts of newcomers by AvA regulars. The best way to do so is by example. Have a good fight with an opponent for a very long time, something goes awry and you collide, his plane is streaking oil, and you seem to have avoided much damage. You have no idea who the player is, or if he is tuned to 200. Over channel one, you send a message: "good fight (enter plane type), too bad about collision go land" This type of behavior is what will bring folks back for more, and even though all of their experiences won't be the same, that one might stick in his mind as a high point. Even better, finding himself in a generous position sometime in the future.
That is how you grow the population in my opinion. The mute function works no matter what setting the arena has. I am no saint either, and there are times that I wish that I had not opened my mouth / text buffer.
A reasonable compromise would be Channel 1 could be disabled if there were a CM present, who has warned the offenders that it would be shut off if they continued abusing it. This sends a clear message and puts peer pressure on the abusers.