Yes, of course they are just excuses. But most people don’t think rationally, they think emotionally. They come up with the opinion they like, and then find a way to rationalize it afterwards. This is as true for the majority of conservatives as it is for the majority of lefties, just with lefties that majority is almost a complete and total majority.
So people are ignoring that Russia’s justifications are just excuses because it is convenient for them to ignore it. They need rationalizations to justify their position, Russia is happy to provide those rationalizations for them so they don’t have to come up with them on their own, and as long as they don’t allow themselves to stop and think critically, they’ll continue on like that until reality slaps them in the face a few more times.
We're supposed to change our behavior because Russia supposedly "feels" threatened, even though objectively, the idea that Russia was going to be invaded by NATO is absurd on its face.