Even if US does not operate any non-nuclear ICBM, there is no way to be sure that the ICBM US is launching against you is actually going to explode. it could be an empty warhead and the ICBM could just be a warning shot just to show China what US can do if China does X action.Your understanding is wrong, and multiple people have already corrected you, which you have ignored. Reality does not care about your misunderstanding. The reality is this:
1. The US does not operate any conventional ICBMs.
2. ICBM trajectories are distinct from shorter-ranged missiles.
3. Therefore if you see ICBMs launched, then you are already sure they are nuclear.
4. Since you are already sure, you retaliate in kind.
Neither Russia nor Israel nor anyone else has ever faced this kind of scenario in reality. As difficult as it may be to accept, there are in fact very good reasons to build silos, and the government—as well as everyone else here—does in fact know better than you.
All big 3 nuke powers have assured second strike capability. Which means, even if there is complete nuclear annihilation of all of China's big cities, China can still retaliate with its nuclear force which are guaranteed to survive such a strike. This is achieved by having road mobile missiles hiding in the mountains, 3000 KM long underground city of tunnels. Then there is also the nuclear subs.
Launching a retaliatory strike is a big decision akin to suicide bombing. You are essentially commiting suicide knowing that the other party will for sure destroy you too. I don't think any politician can make such a judgement call in the current political environment when they know second strike capability will survive.
That's why I don't see any country launching nukes on Warning. They will wait it out, see if this is done in error, see if this is just posturing. Once the missiles hit, bombs explode, then launch the missiles.
Finally, I want to point out that Launch on Warning is NOT China's current posture as verified by many nuclear experts. China does not mate its nukes with its missiles. Could it change in the future? It could. But right now its not. So, Chinese leader themselves are not worried about getting destroyed by Nukes all of a sudden.