Kyivan Rus was an ancestor to Ukraine as well as to Russia. Destroying the monuments in Kyiv and in Chernihiv in particular constitutes wiping out Russia's own history.
I find this "we are all dating back to the Kyivan Rus" narrative very ahistorical and showcasing the limits of applying nationalism to history.
All that you say is true and tested, and the (in modern terms) Swedish origins of Rus'/Россия/Ruotsi/Rootsi and maybe others too is certain. But I'd also like to add some layers of complexity: even before that, those lands were swept and inhabited by various steppe peoples, then the Slavic colonisation came, then as you said there was a big impulse by Viking traders/raiders that, at the same time with Turkic tribes of the region gave life to some forms of Statal entities, then another decisive, let's say "civilising" impulse came from the Byzantine empire, for example the new religion, as this is commonly seen as one of the most important turning points. And then history had it so that over the centuries the regional seat of power moved more notheastwards towards Moscow, and so on until our days. I hope that this sketch is valid, anyway: when we take a closer look history is always a mess.
This is just to come to the point that however intricated these historical events may be, it is still true that many Slavic people of that region regard Kyiv/Kiev under that light as the decisive starting moment of their history. And I think it's not so incorrect in the end: for example, even if the first rulers were Swedish vikings, in the end they were absorbed by the Slavic population, and this is how they identify themselves... even if they started as slaves! So I do not think there really is something ahistorical here: it is just privileging the aspect that today's society deems more important and downplaying the rest. Any starting point is subjective by nature. In my opinion, nationalism kicks in when one has to endure delirious discourses like "there lies the origin of our culture [possibly a true fact], so it has to belong to our nation and we have the right to take it back [a non sequitur
And actually this is the sole reason, in this disastrous situation, I can be slightly hopeful that, despite such alarmism, those sites will be spared; as tsunami said: nobody wants to wipe out their own history. In the end the only thing that counts is how those people perceive themselves and not how history actually unfolded. But since violence can be blind, I am still concerned.
Sorry if I may have sounded pedantic, it was not my intention, it was a tiring day (x_x)