@avoigt was being uncharacteristically hot-headed on this and he may have walked it back in a subsequent tweet. It may be that his background is not in the aerospace industry, so he jumped to conclusions.
In any event, we need to read between the lines and accept that we may never know the whole story.
Shotwell made a carefully worded legal statement. Fact is, if Starlink is integrated into something that is a close cousin to a cruise missile without the cover of doing the Pentagon's direct bidding, that sets off all sorts of legal alarm bells in the United States and internationally. SpaceX is a US company, so has to abide by US laws and treaties. At times, these laws and treaties can be draconian and nonsensical. Starlink kit is good and plentiful and can readily be integrated into all sorts of weapons. So SpaceX needs to be careful with its actions.
Musk made a moral statement, in that integrating Starlink into unspecified offensive weaponry could lead to escalation. For instance, if Starlink kit is found on a drone that hit an airfield deep within Russia that is part of its nuclear forces, things could get ugly really fast. The Pentagon would be even more cautious in the weapons it gives to Ukraine because of these considerations. Altogether, Musk has been extraordinarily permissive.
Neither made a practical argument, such as we have to turn off certain cells in order that Russia can't use the system, even though some Ukrainian troops may find themselves in a dead cell from time to time. But those are background issues.