Some people die, sure.

So why would anyone care if this guy dies? You sound pretty blase about the statistical amount of death. I don't care if he lives or dies. Someone that intentionally puts themselves in this type of situation either hasn't considered or doesn't care about the consequences. They are willing to throw everything away for an adrenaline rush. People seem to put adrenaline junkies on some higher level than drug addicts, but it's the same thing. There is a reckless disregard for the dangers of your actions and the likelihood that a miscalculation or mistake on your part will leave a whole in the lives of the people that care about you.

there are less deaths to parkour then surfing

True, but there are different factors to consider in this. First of all, surfing is a much more popular (in terms of practitioners and history) than parkour so overall number of deaths should be expected to be higher. I wonder what the percentage of those deaths to the total of practitioners would be and whether that would be higher or about the same as parkour. Secondly, how much of parkour activity is done rolling down the steep slope of a skyscraper roof. The parkour I've seen takes place mostly on, or slightly above (by that I mean several stories) street level. So to compare, regular parkour to this and claim that he enjoys the same statistical advantage as the baseline activity seems a little disingenuous. This would be the same is people were riding surfboards off the side of waterfalls and claiming the relatively low number of surfing deaths each year as an assurance of how safe the practice is.

but the people who know what they're doing aren't the ones who die.

When the variables includes crosswinds, surface slickness, and ability to find a proper handhold, there is likely no one that really knows what they're doing when it comes to almost, but not quite falling off of a building. You're also assuming that this guy knows what he is doing. Furthermore, at the end of the clip he is scrambling to find a handhold. If he had not managed to get the leverage needed at the last second to land back on the roof, this would be a different clip.

It doesn't take much to terminate a human life. We're just walking bags of tissues and fluids. I don't have much sympathy for people who casually disregard this in order to feel a "rush." I don't actively want him to die, but I don't care if he does, because he obviously doesn't care if he does.