The general consensus here is clearly that in this situation, there should have been pushback from somewhere. I have seen wrestling at the top of a slide. I understand that posters here all feel that somehow this is a case where spanking would help. I am not so sure.
Another often cited hypothetical in support of spanking is street crossing behavior. Again I have my doubts. Obviously safe crossings are mission critical and nothing is more important. I agree but things are never simple. The goal is rarely to avoid ALL street crossings but rather to avoid all unassisted crossings. So, immediately the plot thickens. My sense is that almost always there are educationally better ways to teach and to develop the relevant skills.
Should spanking alternatives have been used in the case inspiring this thread? If possible, yes. But if patience, time, etc. were not present in abundance, then a simple spanking or spanking might have been appropriate.
What I don't really agree with is the view that this situation called for a hard or high intensity spanking. These should be rare and not used in haste. Several of the comments refer to the recommended spanking occurring at home or off-site from the slide. That would be essential. Is this situation one where all the features of a hard spanking are appropriate? Feeling it afterwards, having a "torn up" bottom, getting it with the belt or getting a hand spanking that was as firm as a belt spanking, ... This seemed bratty but kind of normal and not worthy of lifelong memorability.