Your comment here is way too favorable to the tzar. There was plenty of racism against the non-Russian peoples in the empire. Plenty of pogroms and other horrors committed. The "Great Russians" were very chauvinistic in their attitude towards the other nationalities, and were very privileged in what positions they could occupy, for example. An important part of Bolshevik propaganda was fighting against racism and "Great Russian" chauvinism.

From Walter Rodney's 'The Russian Revolution: A View from the Third World':

There was a group of people known as Russians, who ruled over Finns, Poles, Latvians, Lithuanians, Georgians, Ukrainians, Armenians, Mongolians, and Turks, to name just a few. The Russians monopolized political power and sent their governors and settlers into the countries of these other peoples. As in all colonial states, there was a legal distinction between the citizen (Russian) and the colonial subject. The constitution of Tsarist Russia explicitly based discriminatory measures on the racial or national origin or religion of those affected. It was in some ways like the distinctions made under Portuguese and Belgian colonialism, and under South African and Rhodesian apartheid. In other words, Russian colonial rule hardly differed from that of the Western European powers. The British sent warships; the Russians sent the Cossacks. When its colonial subjects revolted, as Georgian workers and peasants had during the 1905 Revolution, the tsar, as we’ve seen, agreed to a few minor reforms but ultimately crushed the uprising and reverted to the old system of colonialism.

Every colonial relationship in history has involved cultural domination, namely the imposition of language, religion and way of life on the subjugated peoples. In the Russian Empire, there were numerous other religions apart from the Russian Orthodox church. None of these were respected. The Catholics in Polish Russia were persecuted. The Jews were hounded wherever they were found, especially in the Ukraine. The Muslims were treated as enemies of Christian civilization. And those elements of the population who believed in their own family gods and traditional religion were the most despised of all, in the same way that European missionaries came to Africa and denounced African religion as devil worship and black magic. […] When faced with a more technologically advanced culture, such groups were victims of genocidal policies.

Pushkin's ancestor was a curiosity gifted to Peter the Great.

Sort of a house slave treated well due to his rareness.

Russian servants would be treated worse due to there being a bigger supply of them (some would, though, instead of peasants become soldiers of his toy regiments and sometimes more).

Then at some point, yes, Peter, consistently with his other hobbies, decided to free him, make him an officer, put him in uniform etc, ultimately marrying him to a girl of noble descent and making him a noble himself, of course.

That's not quite the same as not being racist.

Though some ethnic cleansing had happened in the Caucasus.

That's usually called genocide.