Thanks for posting this, very interesting. In the Watchtower's defence the document does say twice that the society 'does not support either party in this case'
However their arguement is that it would be wrong for individual JW to have to pay sales tax. The arguement should have been about whether the Watchtower should pay sales tax. Although individual JWs may well give away some literature, the society had a fixed price that they charged the congregation members and there was no getting round that. I think the society realized that it was going to affect them rather than the individual JWs which is why in the end they went to the donation arrangement.
Talking about the affect on individual JWs was simply a redf herring which the court saw through.