Not true if a single .50 cal round in the right place can detonate all of your missiles.
I have seen many vessels with combat damage and a .50 caliber hit on a missile would not cause a detonation because most ammunition of this caliber does not have an explosive filler. Also, the missile's Safe and Arming Fuze would prevent this kind of detonation.
However, take a direct hit from an anti-ship cruise missile and all bets are off. Several hundred pounds of high explosive WILL ruin your day. Sometimes you can take several hits and survive because your luck hasn't run out.
On 17 May 1987, USS STARK (FFG-31) was hit by two AM39 Exocet missiles fired by an Iraqi F-1EQ “Mirage” fighter. Both missiles impacted at or just above the waterline, portside, below the bridge. Fortunately for STARK, neither missile resulted in a high order detonation of the 364 pound warheads. Major damage and fires were mostly from the mass of the missile airframe and burning rocket motor propellant. One of the missile warheads was found mostly intact 20 feet away from the forward Standard SM-1 missile magazine of 40 missiles. There were 37 crew killed and 21 wounded in the attack.