Aggression would be invading Russian sovereign territory.
It never happened.
What did happen is that Russia invaded Chechnya, Georgia, and - in 2014 - Ukraine.
Your argument is akin to saying that Hitler would have been acting 'aggressively' in the 1930's if he never invaded any of his neighbours sovereign territory and he was forming a defensive alliance.
Small European nations have been concerned about Putins military build-up and his invasions of neighbouring countries. When you have a menacing power right next door, which has form for invading and subjucating nations like Poland, Lithuania, Estonia, Finland, Latvia etc, then you'd want to be part of a defensive alliance.
It's all very well for you sitting in the west with a heart full of hate for NATO; you've never been invaded. You don't know what it's like to have a menacing autocratic state like Russia just across the border. You can't tell a Finnish person that they shouldn't be afraid of Russia when their countrry has been invaded by Russia previously, and they witness Putins behaviour.
