Etiquette serves two conflicting goals. One is to treat people well, and the other (perhaps the thing that distinguishes it from kindness) is that it gives people the tools to treat you well.
There is no time or place more conflicting in this than when dealing with drunk people or hung over people. Drunk people have no kindness – or, at least, more limited kindness. If there's anything I'd like to impress upon people, a small fragment of wisdom I've won from life, it is that kindness is an active process. It requires the attention to notice how people are feeling and the dedication to see it improved.
In this sense, it is both hard to blame a drunk person – because their intent was (usually) good – but also tremendously easy, because if their intent was to be a good citizen, neighbor, or friend, they would not have drunk so much as to be incapable of the task.
I think it's pretty clear I don't drink alcohol. Let me be explicit: I am extremely judgmental of people who drink to the point of carelessness. To choose your own momentary happiness over those around you is a selfish act, and to alienate those who choose otherwise (which I suspect recklessly drunk people don't notice or care that they do) shows the heart of a bastard.
Most people drink only a little. But those who don't are frequent enough to be concerning.
But the morning after, hung over people need sympathy. The same sympathy they denied others just hours previous. They've oddly vulnerable, and etiquette says we should be accommodating of that. Surely the worst possible thing to do would be to escalate their behavior.
I find myself having abandoned the subtleties of normal etiquette in some scenarios. The too-tired "you're speaking too loud" when you're speaking normally, the admonishments for making noise at the "ungodly hour" of 9am. It can be a bit too much, occasionally, and I find myself wanting to calmly tell them I am disgusted by their behavior, their lack of capacity to apologize for their breaches of etiquette and presumption they shouldn't.
I have not done this, never. And I probably shouldn't, most of the time. But all systems require balance. How can we learn to be better if people politely conceal our minor misdeeds? Am I complicit in the bad behavior of others because I failed to be honest about how they've harmed or even bothered me?