And the difference between an airliner and a cruise missile is? And the difference between a rocket and an ICBM is? By your argument, we wouldn't be using those technologies. And yet we do, on a daily basis.
The known reaction time window of a ballistic missile is ~15 minutes (for russia) to 30m (for the USA) and is already too short, leading to near russian launch at least once that we know of.
The reaction time for any space based weapon is down to minutes to seconds. Putting them into orbit is already a war declaration.
This is not something that will be allowed without heavy international control and multi national regulation.