I think the name is good. It is a little bit provocative and may capture the attention of the media in situations where a more subdued name would just be ignored.
I think it may require some explaining, but it is better to have to explain the goals of the association than to have it overlooked.
I definitely the Watchtower Corporation is evil enough to deserve an anti group.
I do think the name could be a liability for some forms of activism, but this association doesn't have to tackle everything. There is plenty of room for other groups to form with slightly different goals that could adopt more friendly names.
Although I also like Stonewall's suggestion of "Association Against Watchtower Abuse".