And of course, what the fans who insist on this myth of the Black Hat Typhon Pact consistently ignore is that the first official act of the Typhon Pact was to withdraw the Kinshaya forces from the Klingon planet and apologize for the aggression. The Kinshaya acted on their own; the Pact as a group pulled them back.
As I suggested above when alluding to initial United States policy after World War I, readiness for defense does not imply that the power to be defended against is a villain - it doesn't mean even that they aren't an ally. The Pact, of course, is not an ally. It is composed of nations generally individually hostile to the Federation (the Gorn being a notable exception); one of its members appears to be gripped by religious militantcy, which has never ended well. A Federation that failed to arm itself while seeking peace - and to arm itself sufficiently well to ensure victory - would be absurdly foolish.
Disarmament without rapprochement is the graveyard of good intentions. It crippled the European powers when Germany began to rearm after World War I; it cost the Americans dearly in World War II (the Japanese Empire began to ignore the arms restriction treaties much earlier than did the democratic powers - as nations taken over by militants tend to - and the United States almost set them aside too late to be of any use in capital ship combat in World War II); it nearly cost America its independence in the War of 1812.
Interestingly, the Republicans made many of the same arguments in the late 1700s and early 1800s that you make here: establishing martial force would invite war by suggesting hostile intent where none existed, there was no reason to expect attack from powers that bore no inherent ill will, etc. The Federalists made the counter argument, insisting that naval power was a necessary hedge against the unlikely, a deterrent to other nations' estimate of the probability of success in war. Eventually, the Republicans took the country into a war that the Federalists opposed, with the small force the Republicans had devised, and the United States was very nearly soundly beaten by the small squadrons of battleships the British could afford to divert from the Napoleonic Wars. The United States survived almost solely because a quirk of geography enabled us to bring roughly equal force to bear in the crucial theater of the war (neither side had an existing fleet of any size on the Great Lakes, and neither could transport existing ships there).
Disarmament - or under-armament - requires rapprochement. The British were able to withdraw the Royal Navy from the Caribbean because they had come to a mutual understanding with the United States. Later, the French were able to withdraw their battle forces from the English Channel for the same reason (their understanding was with Britain, previously - and recently - their mortal enemy). Europe is demilitarized today because of understandings reached with the Germans, the Turks, the Russians, etc.
Even in Star Trek, disarmament followed detente, rather than preceded it. As we saw in Redemption, the Federation was able to withdraw its border forces after it and the Klingon Empire came to terms of understanding - and as we saw in The Undiscovered Country, the Federation was well-prepared for the possibility of war with the Klingons while that war's possibility existed. And Star Trek went to great lengths to assert that the Klingons, like the Russians in the Cold War, were simply our adversaries, not our enemies.
Imagine you're, say, a Klingon looking at the formation of the Federation in 2161. Would you see the lofty and peaceful intentions, or would you just see that four species you've clashed with in the past have just formed a powerful alliance that you need to be worried about? Whatever lofty intentions the UFP's founders may have had, they were also surely concerned about being militarily strong enough to hold off Romulans, Klingons, and the like. So the way the Klingons or Romulans would see the union from the outside would be very different from how the people on the inside would see it. By the same token, you can't assume that the way the Pact's formation looks from the Federation's perspective is the same way it looks from the perspective of the Gorn or the Kinshaya.
I imagine that the Federation would seem much like post-unification Germany seemed to the extant European powers (Earth would be Prussia in this example): A somewhat backwater, if occasionally troublesome region newly united and suddenly potentially dangerous (particularly given the military successes enjoyed by the Earth/Prussian forces in the recently concluded war). The comments of Klingon diplomats in The Undiscovered Country and The Voyage Home suggest that the Klingons saw the Federation along those lines in the late 23rd Century, at least. In Klingon eyes, the Federation was "a homo sapiens only club," the Vulcans its "intellectual puppets," and the Federations rhetoric hollow - typified by the notion of "inalienable rights."
The Klingons were wrong, of course, as were the French about the Germans under Wilhelm I, but in both cases military readiness protected the states from aggression: the Germans from Napoleon III, the Federation during the brief war in Errand of Mercy. (The Federation retained strong military capability; in The Undiscovered Country Starfleet professed that "we can clean their chronometers" before the President chose diplomacy).