It's interesting that the first sentence on their homepage includes the statement "experience a European-style cycling event" - we've ridden our tandem in several European events (in France, Italy, and Switzerland) without any mention that our tandem was causing problems with safety. One or two of them even had a special classification table for tandems.
If you can't get the organizers to listen to you, then I would try to contact Axel Merckx directly and ask him whether he is happy to have his name associated with an event that forbids tandems - he may not be aware of the issue.
The rule is certainly not caused by the event being part of the UCI World Cycling Tour series, because one of our local events is also part of that series, and it does not have a ban on tandems. If your pleas to the organizers fail then I would therefore try to contact the UCI and see what their opinion is on the matter - if they disagree with the ban then I'm sure that they could exert the necessary pressure.
Last edited by Chris_W; 06-28-12 at 01:18 AM.