"Tell people something they know already and they will thank you for it. Tell them something new and they will hate you for it."
George Monbiot
Well, all ideas are "ridiculous" to the extent that they are capable of being ridiculed.
Ideas usually run through a certain life-circle, yes... They either become forgotten, or acknowleged for a commonplace with time. The idea contesting the flatness of Earth, the evolution theory -- all of them were "controversial".
The notion of Gays being easily exterminated if gathered in one place has two aspects: the military one and the social one.
The military aspect is simply the fear that a Gay city could become a target for a nuclear bombing (anything else can be dealt with more easily). Clearly, being nuked is a sort of attack which can eradicate any city entirely. And yet this happened only twice in history that this weapon was used. Why so? Because a nuclear strike presupposes three things: a) the ability to produce such a weapon, b) the willingness to use it, and c) the absolute certainty that the assault will not be retributed. I can imagine dozens of strategies to eliminate at least 2 of these presuppositions in any hostile nation.
The social aspect implicates that heterosexuals really do hate us to the extent they would attempt to exterminate us despite losses of personnell and material on their side. Need I say that the mere acknowledgement of these murderous intents reveals little trust into the results of the "equality struggle"?
On a more generall level, I must say that there is a certain fear of living, a kind of self-containment wide-spread among our people. There is this fear of taking the life "by the horns", of unconditionally claiming one's birth right and taking advantage of everything the world has to offer. Certainly, an indipendent Gay state might have enemies, but
so does every other state too, you know? Each and everything in this universum has a certain price to pay for if one desires to take advantage of it. Visibility has its price. Coming out has its price. Freedom and a self-determined life have their price, too. The price is the inconvenience of assuming responsibility over oneselves as adults.