Russians are a minority in Estonia and Latvia

Any day Russia can say, "the Latvian/Estonian goverment is mistreating Russians, and so we must attack your government to save the Russian minority"

And then the minority will decide if that's true or not and whether they'll take part in the protest against their government's "injustices" which may or may not exist.

Hence it is important to treat your minorities with respect and grace them with representation in every possible sphere. So that when another country tells them "You're oppressed, we have to save you." they can say, "We're not."

Hence, a country's minority isn't a threat to the existence of the State. It's a challenge. Deal with it.

This is true not just for ethnicities but every sort of community we can think of.