The traditionnal ecumenist argument : we are witnessing....bababababbababa.... Did the apostles invite heterodox to witness their services like spectators?
Yes. They were called Emperors. So long as it was not an emperor who was completely anti-Christian (e.g., Julian the Apostate), Emperors had free reign to do whatever they wanted in the Church, including going back by the altar. There were a few fiery exceptions, such as St. Ambrose refusing Theodosius entrance to the Church, but by and large this was the exception and not the rule, even among saints.
Today, on the other hand, rather than an imperial government set within an agricultural culture, we instead have a pluralistic, urbanized culture with a Republican/Democratic government. Completely different things, and I believe reason enough to give more leniency. The strange part though is that we are actually, comparitively speaking, more careful. We now allow non-Orthodox to see the entire service... yet in regard to letting non-Orthodox and non-males by the altar, we are just as strict today.
I don't think you should deride Churches for such things happening today unless you would also be willing to go back and deride St. Nektarios of Constantinople, St. Photius the Great, etc. for allowing emperors with shady motivations and even shadier deeds back into the holiest of places to sit and daydream about conquest. These representatives may indeed never change their faiths, but playing the isolationist won't help either. Jesus Christ said to let our light shine, and not to put it under a basket. We should not extinguish our flaming candle by slamming the Rudder down onto it.