Countries with small arsenals and no ICBMs or not enough to survive a first strike, even conventional, still lack a proper deterrent. Iraq under Saddam was bad news but not a license to do whatever he wants. In fact, having nukes and invading another country who has allies with nukes is a great way to end up getting nuked after inadvertently starting a larger conflict.Deterrent, not deterrant. Also, Yes, countries without nukes are more vulnerable to attacks. Just imagine what would have happened had Saddam Hussein got nukes before he invaded Kuwait. In such a scenario, the West might have been much more hesitant to militarily intervene.
Its like being one of few tough guys who primarily use fisticuffs but getting a gun. You're a badass until you get into it with someone with their own gun, especially someone with more guns, better guns, who is highly skilled with them. Suddenly the idea of being a gun fighter doesn't sound so hot.