In Russian, there's a distinction between русские (ethnical Russians) and россияне (Russian nationals/citizens) which doesn't map to English well - it's Russians either way in it. This slogan implies the former (ethnical Russians), and was declared extremist long ago, for a reason.

This distinction is a very frequent source of misunderstanding for both native speakers and English speakers, as Russians might hear one where you imply another, and vice versa.

> Sounds like a reasonable thing to say even if you disagree.

pretty sure many Turkic, Mongolic, etc. people lived in what is now Russia long before a Russian state existed.

That's treating the phrase an an ethnic thing, you might say "well clearly they mean Russian as a Nationality" but in that case Russia already belongs to Russians.

This slogan implies that ethnic minorities (19% of Russia's population [1]) are not welcome in their home country.

[1] https://en.wikipedia.org/wiki/Ethnic_groups_in_Russia

Russia is a multi-ethnic country and slogans like that are destructive.

This is a slogan used mostly by Russian neo-Nazis, but quietly supported by sizeable parts of general population.

It’s has a few connotations. The mildest is proposing to throw all colored people out of the cities. The most severe is to exterminate them.