Dude. There are a multitude of reasons why he might want to travel alone. Whatever those reasons may be, the act of doing it is in no way stupid. He was on one of the most populated hikes in America. Read the first line of this trail description. 3 million people a year and there are all of about 4 hikes in Zion. Sure it can be exceedingly dangerous in bad weather, but he checked the weather beforehand. There were a multitude of people along the way. Look at the pictures. If this was some random and difficult hike in the backcountry I would be singing a different tune. But it's not. The risk behind this hike was small. We all take on levels of risk that are acceptable to us. Any of the things you mentioned can happen anywhere. Anyone with half a brain, when attempting something solo, adds up the risk levels, and says "yeah I can deal with that". He did a fine job of that and came out ok. Jumping off the rock was fucking stupid but everything else was alright. There's no need to discourage people from being so risk adverse.