Sure, we should act according to Putin's whims. So if Putin says 'do not help Ukraine or else' we stay. If Putin invades the Baltics, well, no ICBMs, right. If Putin nukes Ukraine we do nothing (no ICBMs right?). Can't we just surrender the world to him to stop these ICBMs?
Good thing we didn't have this attitude during the Cold War. We can help, and we should not going to listen to a non-ultimatum which hasn't been even given.