I looked into the Crimean Tatar issue and yeah the evidence is damning...
From the Human Rights Watch: "crimea-persecution-crimean-tatars-intensifies"
Since 2015 a grand total of 26 Tatars have been convicted and jailed. They are all part of a group, Hizb-ut-Tahrir, that has been designated as a terrorist group in Russia, Germany and several others.
Some of the detainees do not deny some level of affiliation with Hizb-ut-Tahrir, but all deny any involvement in a terrorist organization. Under Russian law, participation in a terrorist group (article 205.5, part 2 of the Russian Criminal Code) is punishable by a prison sentence of 5 to 10 years.
Even by the HRW's own words these people have broken the law.
Not really mass persecution, is it?