Terrorism is any (unlawful, violent) act that uses fear to achieve a political result. Personally, I don't see how yoga is violent or directly instills fear to any particular target of people. However, if somehow it can be legitimately proved that a certain aspect of yoga did truthfully fit the aforementioned criteria (or was somehow intentionally used to the advancement of such a cause), than terrorism is terrorism.
Yoga is an exercise practiced by many to help them relax. Yoga is not terrorism anywhere, not even in Russia. Russia should have bigger problems to worry about then people practicing yoga. The Russian government should welcome anything that can improve the lives of its citizens, because many Russians live bleak lives.
No, yoga is not terrorism. Yoga is exercise. It's about quieting the mind and strengthening the body. It has nothing whatsoever to do with terrorism. The problem in Russia is that the powers that be are trying very hard to control the population at large. They want to dominate. They want the people to be meek and submissive. Now we've got Trump wanting the same here in the United States. No thank you. Nobody should be arrested for teaching something as empowering and healthy as yoga. That's absurd!
Seriously! Yoga! The whole situation smacks of something someone would read in the papers during the Cold War. Assuming the yoga is being practiced in much the same way as it is in the United States, it is difficult to see how the practice is subversive or "terrorizing" anyone. Maybe if it was nudist yoga.