Everyone is responsible for their own actions- otherwise you get into an endless spiral of "I did that just because you did the other thing first, so it's ultimately your fault".
Why are you then mentioning Ukraine in this context if not to send us into this endless spiral?
And we know the Russian ship cut the data cables, so if your assumption was true, it means Russia also cut nordstream. So why bring up Ukraine cutting nordstream? It makes no sense.
You are the one picking and choosing here.
Even if it was Ukraine (it wasn't - read this about Putin friend's tanker https://www.businessinsider.com/nord-stream-mystery-minerva-... , tankers seem to be the favorite Russian sea-platform for sabotage), the Nord Stream majorly - 51% - owned by Russia thus it would be a valid target for Ukraine.
>You can't be indignant for one sabotage and ignore the other.
You can and should. There is huge difference between valid targets and invalid ones. By attacking Ukraine Russia made itself into a valid target for Ukraine. Finland and Estonia aren't valid targets for Russia.