In the article, which you posted the link to, the talk is about commercially used property but not about religious activity. If we would consider the possibility to tax the religious activity as well I think it would look strange enough since all the money which come to church are the "charity" by those who give money. Something like to tax homeless for those money they are given on a street. Well the amount of money got by church and a homeless is extremely different but does it make sense?

On the other hand would not taxing church automatically make this church an official religion in the state?

As far as I concerned in Russia church doesn't pay taxes. As for church going to politics what I see is rather politics going to church. During last years all the Russian party leaders along with the president and the prime minister were visiting church quite frequently as a place to show up their "loyalty". Their visits were covered by TV more than political meetings.