I'm not sure who would say that it was to 'stop NATO aggression', but it's not hard to imagine it as a some kind of response to NATO's continued expansion around them.

NATO hasn't been in any direct operations against Russia but they have been involved in the ME where they have been active.

I think of it a lot in the same way as the US's pacific ocean and Caribbean territorial expansion and involvement in central america as a response to the Cuban Missile crisis and Soviet posturing.