Interesting article. I admit, when I think of events like Assisi, it makes me uneasy.
When it comes down to it, decisions to hold events like that are a judgment of a human being and may or may not turn out to be prudent–even if the intentions were best.
If you read Pius XI’s encyclical Mortalium Animos he warns against even participating in events like that with non-Catholic Christians and goes on to lay out the dangers.