I doubt you'd feel the same had you lived when the Ottomans came for Rome.
No, you'd be demanding people fight to the last man.
I can give an example of how the justice operates.
Let's say a man decides to break into his neighbor's house, and to rape her.
He rapes her all night. Then he stops and goes to the bathroom. The woman takes a knife from the kitchen and stabs him repeatedly. Killing him.
The police arrives and arrests the woman.
According to some, evidently, this woman is guilty of killing a man and what happened before she took the knife and stabbed the man, is irrelevant. So the woman is a murderer, and the man is the victim here.
Same as for Ukraine. What happened before Putin invaded, is irrelevant and unimportant to some.
Putin is the perpetrator. Period.
That's not how justice operates.