Well, I am currently sleuthing my rather rich and eclectic family tree, and it turns out that ‘Saint Basil’ a.k.a. Vladimir I ‘The Great’, Prince of Novgorod, King of the Kievian Rus/Russians is one of my 27th generation great-grandfathers - this being so I have done some research on him.
It appears that he himself was a convert to Catholicism, and like many converts, could be very/robustly zealous of his new found faith. He greatly expanded the family kingdom and took it from the Black Sea to the Baltic Sea, at the same time expanding and securing the eastern and western borders. As a way of strengthening unity/identity within his expanded kingdom he ‘encouraged’ his subjects to conform to the one newly established faith. It seems that the robustness in his politics and on the battlefield also followed into his religious zeal. I find it more than likely that it was not just to the pagan religions he applied extreme options to, but also to such as the Jews. Sorry about that!
p.s. If I remember correctly the 1,000th anniversary of his death was in 2015.