May I know what is the point of boycotting those casinos? Do you think the Russian economy will be affected due to this? Just the owners of those casinos will get hit who may also against Putin's decisions. Anyway it's good to know the casino operators from Russia in a list and there are some scam sites are there should be avoided at any cost.
It may not damage economy, but people want to express their solidarity, mutual support. There are thousands of people in the streets in Europe, America, Canada which may not change anything but I think its a sign of solidarity.