[Protagoras]

Is there any point, at all, where the actions of the person who imbibed are anyone else's business,

It would not be the business of government.

or would that be only if s/he did something that involved/harmed another PERSON?

"Involvement/Harm" is not the standard. If a person's rights have been violated by another, it becomes government's legitimate business. Not unless or until.

[Froufrou]

I'd like to know your take on the Gay Pride Day indident in Philadelphia, when charges were brought against some 13 anti-gay marchers...?