That's about 5% of your alliance. It was also two-thirds of your nuclear armed nations. And over a rather close period of time. And two of the CDT nations eating nukes weren't nuclear.
I'm not exactly sure how 4 is greater than 19, but there you have it.
I believe the "If you don't want a war to go nuclear, don't say you'll keep it nuclear and then first-strike your opponent" conundrum has been addressed above.
(To clarify, I realize that this is TE, and not "serious business," but I feel I should remain at least partially in-character. )