The issue here between the two sides seems to be a difference of moral stances.
Catholic Scientist seems to be looking at the how the Cross helped a grouo of rescue workers, and their actions and what gave them the strength makes the Cross enough to include. I guess that if any other religious symbol was found at the time and gave strength to a rescue effort, he'd support that symbol too. I haven't heard of any others found, so that is likely why only the Cross has been mentioned.
Now the other side, maintained by enough of you that I won't bother naming, appear to be taking a more consequencial look at the moral dilema. Puting up the Cross and no other may well not be intended to show religeous favouritism, but this isn't just about intention, it's also about consequences. It's easy to see how visitors may take the Cross to mean more than the stated intention.
For me, the consequences are more important.