In a passing thought I was to call this Disclosure Fantasy, and it's certain to have at least a couple or so fantastic items, but with plenty of people's accounts of high strangeness, who's to say the basic idea isn't possible? This is what I envision as the ideal mode of formal Contact; by televised speech (in spoken-not-telepathic English) by a bonafide nonhuman:
First, I'd be completely comfortable with a woman, and I hope I'd be wrong, but I'm pretty darn firm that the emissary must be a man. This is obviously because of the sizable percentage of male chauvinistic-supremacist brutes who understand (basically) only brutality on this rock. He should be, if not one of the reported-or-alleged (very tall) "Nordics," one who looks more similar to humans than the too-jarring greys, reptoids or insect-like beings (obviously); yet couldn't be seen walking in Times Square today...
Speaking of which, that would be the perfect spot for him to make his entrance. After he pulls up in his vehicle, he walks to the ABC TV studio and makes the short statement. [That's a far more (properly) of-the-people place than some stuffy, official Washington location]. He says:
"Hello New York City and planet Earth. My name is (Mezgik or whatever). My people believe your species is evolved enough to know the truth, but you'll need some common sense items to get through the transition.
"We're here to confirm your planet, and yourselves, in peril. The mixture of population growth with industry as you know it isn't a longevity model, and you have no moral or logical basis for continuing your crass consumption. It's time to let cooler heads prevail and, as you say, lay down the law in the most bodacious way.
"The specifics, in terms of colonization of other worlds and, gulp, yes, mass sterilizations, will be brought forward in the next few days. We believe you're evolved enough to solve problems the civilized way. Meanwhile, I'm off to see if there's a better club with live rock and roll than the ones I've heard so much about in Austin, Texas. Toodles until next time."
Depending on how easily he's able to move through the crowd back to his (road/ground) vehicle, which is seemingly not likely easily, there may have to be (a) small drone(s) near him to deliver electric shocks (like a force field) for dispersal; and probably whatever other anti-sniper and assassin implements and/or personnel.