G'day Thom,
Is it ethical for a Wiki editor, who is also an admistrator, to edit both sides of an issue?
If that editor is a good Wikipedian --- and, being an administrator, we should hope he is --- then it is entirely appropriate for him (or her) to edit any article he (or she) damn well pleases.
It's called "writing from a netural point-of-view", and some of us pride ourselves on our ability to do just that.
You might as well ask if it's ethical for me to edit an article about Manchester United FC ...