I'd love to know how Kai Kracht has concluded that the verse about the Chechen was not part of Lermontov's poem?
In my copy of Mikhail Lermnotov's poems and the novel "A Hero of Our Time" (biblioteka vsemirnoj literatury; EKSMO, Moscow, 2002), the poem has that line.
"Po kamnyam struitsa Terek,
Pleshet mutny val;
Zloy chechen polzet na bereg,
Tochit svoy kinzhal;
No otetz tvoy stary voin,
zakalen v boyu:
Spi, malyutka, bud spokoen,
bayushki-bayu."
This is, after all, the Cossack Lullaby. WITHOUT debating the rights or wrongs of the Caucasian Wars, the Chechens were a very real danger to the Terek Cossacks. This bit has the mother comforting her son that although he is facing the dangerous Chechen, the father is an experienced warrior. So unless someone can show that the verse really wasn't part of Lermontov's poem, this iis nothing more than a PC clean-up.