Mark,
In reply to your reply, I would just like to say that for one, I am a vegetarian, in doing so I abstain from all meat products, which shows the degree of compassion I am willing to show toward animals.
In regards to all your other points, they are fairly off topic as the letter was about duck hunting, not about hairspray. (filler)
According to Professor Richard Kingsford of the University of NSW, the decline in ducks has reached 60% between 2007 and 2008
Make a point that protected species are also culled during the hunting. And that noone is a 100% accurate shooter.
And maybe just to stick it to him, with the smart arse comment about you not emailing every person in australia, find a petition which condemns the duck shooting, or something simliar.
As you can respect my compassion, I can generally assume that you yourself have some; in your heart you should realise that it is hard to convince anyone that this ugly spectacle has anything to do with sport. The violent killing and maiming of native birds and animals can no longer be regarded as a legitimate recreational sport.
I don't care if you use it word for word, but I hope I've given you something useful to work with! My only other suggestion would be to use statistics which can be backed up, and from a non biased website if possible. By the sounds of his reply he is going to use any sort of flaw in your letter as cause to argue a point.