So, your argument is that people arguing in the 1990s that expansion of NATO was a bad idea (because said expansion would encourage Russia into hostile actions) is justification for Russia to enact said hostile actions in 2014 and 2021?
It sounds like you're basically saying that, if someone threatens you with violence unless you adhere to their demands, not adhering to those demands is justification for that violence. So you should give up your lunch money under the threat of a bully, and the bully is right either way - in taking your lunch money, or beating you up for not giving it up willingly.
My argument is that all violent thugs are cunts. Plain and simple. There is no valid justification for violence, unless it is to prevent a direct threat of violence against yourself.
That is to say, if someone comes at you with a weapon and clearly indicates they're going to kill you, it is reasonable to kill them first. "Expansion of NATO" does not, in any way, meet this bar.
To take the analogy further, NATO is merely a group of countries banding together and saying they won't let bullies get away with being violent cunts. If the bully wants to attack one of them, they will all respond together and overwhelm the bully. The bully is now just cowering and crying fowl merely because they're now the smaller, more vulnerable one. When the group is actually making no threats whatsoever, other than to rightfully defend themselves and prevent harm against themselves.