The most common thing I hear, by far, from members of the public at search and rescue fundraisers is, "why do you go to all that trouble for stupid people?" It's a question almost always delivered with the self-satisfied smugness of someone who has no idea that they're already suffering the atrophying effects of not venturing outside of familiar territory often enough.
McCandless surely made mistakes and errors in judgement. He certainly underestimated what he was getting in to. In that, he has something in common with hundreds of thousands of casual hikers, mountain bikers, kayakers, and visitors to national parks every year. There are vanishingly few entries in the annual Accidents of North American Mountaineering where the people involved are unimpeachable in terms of their preparedness or skill. In almost every case, there's something that someone could point to that the victim did wrong, and if not, then there's always the fallback that they were dumb to be doing it to begin with.
If he hadn't died, nobody would know his name. Statistics caught up to him. Statistics will catch a few other people every year while far more visitors to the same area will escape without consequence.
The dynamics of this subject on HN in particular are really sort of obvious, given that McCandless has come up at least half-a-dozen times on HN over the years, a site not known for its enthusiasm for the outdoors. The treatment here is often about as embarrassing as someone might imagine the topic of machine learning to be on a forum for mushroom pickers.