That's in violation of Russian law. In 2013, Vladmir Putin passed the “gay propaganda” law. Although the law is fairly ambiguous as to what is actually covered by its regulations, part of that law prohibits public performers from doing same sex kisses.

 

Violation penalties include: Russian citizens found guilty can receive fines of up to 5,000 rubles, and public officials can receive fines of up to 50,000 rubles. Organizations or businesses can be fined up to 1 million rubles and be forced to cease operations for up to 90 days. Foreigners may be arrested and detained for up to 15 days then deported, or fined up to 5,000 rubles and deported. The fines for individuals are much higher if the offense was committed using mass media or internet. The German band haven't suffered any repercussions yet.