Russia has been trying to eradicate the Ukrainian language since Catherine the Great

Even if that was true and not some harebrained ahistorical overgeneralisation what does that have to do with how the Ukrainian state treats it's Russian-speaking population? We are talking about an Ukrainian law, imposed by the Ukrainian state on Ukrainian citizens living on Ukrainian-controlled territory. How is trying to eradicate the Russian language in Ukraine preventing the alleged Russian policy of eradicating the Ukrainian language in Russia? How does one wrong justify another?

Ukrainian has been an official minority language of the Russian Federation since the breakup of the USSR and schools in Russia's new territories are teaching an Ukrainian-language curriculum to students whose families so desires. There's probably plenty of bad things to say about the Russian education system but giving a language you are hellbent on eradicating official status and teaching it at schools seems like an odd thing to do.