Complain to your bishop, in writing. Sounds like an event for the parish center not the sanctuary.
I think I will. The pastor at the Cathedral is totally clueless and came from a university parish with a heavy pro-gay agenda, hence his fondness for the Episcs. In addition, the music director he chose thinks of the Cathedral as simply a performance venue. And they just got a new "liturgist," a flaky lady who had some sort of "service" for All Souls where she came out in a black dress, set the Paschal Candle in front of the altar, and stood there staring at it with her hands out for about 5 minutes before she grabbed a bowl of incense and waved it around. Our bishop is very orthodox, but he is not at most functions in the Cathedral, so I don't think he's fully aware of what's going on.
Liturgical flakiness aside, I think it is highly inappropriate to have a group like the Episcopalians - the branch in my town is not even one of the conservative sets - on our altar. They share none of our moral teachings anymore, doctrine went a long time ago, and "Mother" so and so should not be parading around any Catholic church, much less a cathedral.