Apparently they could shoot them down with patriot missiles except the US doesn't want them used in Russia territory. I'm not sure of the virtue of making Ukraine fight with one arm behind it's back where Russia can destroy all it can in Ukraine's territory but they are largely restricted on striking back in a similar way.
I mean I can understand the desire not to escalate but it would seem reasonable to reciprocate whatever attacks the Russians are carrying out.
Russia destroyed 2 of Ukraine's Patriot launchers, causing Ukraine to decide to stop stationing them on the front lines. (Now they protect Ukrainian cities.)
I think the argument you want is that if the US gave Ukraine a lot more patriot launchers, Ukraine would probably be willing to risk a few of them on the front lines.