I don't think it needed to be handled at all. We don't moderate any other spam in CN, despite it being full of it.
That's not strictly true. If a bot were to post an ad we would remove it. Regardless though, can someone link some examples of the offending posts? I clicked around for a moment until my CN threshold was passed and didn't find anything overtly spam-like or "browser-crashing."
Personally, I generally fall (perhaps in a self serving way) on the side of the person moderating in these cases. If they deem something to be spam, then I agree that a short ban (1 day) is fine. In the vast majority of the cases it's a one-day troll looking for a couple laughs and the short ban solves the problem. In my opinion, the issue here is that the person with the moderating powers may have misjudged what is or isn't spam, not that the reaction was excessive. However, the abilities to moderate an issue are given based on what bits of a person's character can be gleaned from how they comport their online-selves. We should trust that character to administer judgment if we trust them enough to give them the power to do so.
In this case, it was an administrator that made the call, which dredges up the question of should admins be moderating? As it stands, they can moderate and I have no issues with them continuing to do so. If you don't give the people moderating a bit of leeway to make judgments then you are hampering their ability to do so. If what I understand is true, the offending poster was spamming with an intent to cause harm, then I don't think that Junker was in error giving out a short warningless ban.