It is not a 'cultural genocide' to send Russian speakers, who have family ties to Russia already, back to Russia. Kids born in said nations can stay, I guess, but you best bet the security services will watch them like hawks because of Putin's antics and if they step out of line goodbye citizenship.
There's a number of problems here.
First, taking a dictator's excuse away only helps for as long as it takes him to come up with a new excuse. Usually, that'll be at most the length of one staff meeting. So your idea of kicking out Russian-descended people is a bad idea, because
it won't work.
Second, you're ignoring both the rights
and the agency of those people. You're certainly going to destroy any loyalty they may have had to your nation, and setting them against you.
Third, you're giving the dictator a
new excuse to invade. As you are
demonstrably trampling on human rights merely because of a person's ancestry, he can simply use that as a
cassus belli to invade and give back the citizens you exiled the land/homes/property you took from them.
Fourth, there's a much simpler, better way to deal with this. Go door-to-door with your expatriot-descended citizens, and ask them a simple question. 'Do you think that your ancestry means that Russia should control this territory?' If they answer no, then you've got your PR counter to the dictator's excuse. If they say 'yes,' then you've identified a traitor; if there are enough people giving this answer,
then you start looking into legal proceedings targeted specifically at those who've made it clear they're loyal to a foreign nation, to expel them and strip them of their citizenship, because
by their own admission they are loyal first to a hostile power.
The idea that you've proposed here shows how you still, at a fundamental level, think like a leftist. You want to do things based on group identities, you're ignoring personal responsibility or lack thereof, and you want broad, sweeping policies that will cause harm without even solving the problem they're supposed to deal with.
And more than else, this shows how you still think like a leftist, because if you actually thought the issue through for five minutes before deciding what your stance was, you'd have come up with a better solution, that wasn't based on overly-simplistic thinking.