This is way more than just defamation. For example, among many laws passed in the last 6 years or so, one criminalizes "public incitement to perform actions that violate the territorial integrity of Russia". In a twist of irony, given the recent events, a person was convicted under that law back in 2010 for distributing leaflets in his community which asked people whether they would be interested in holding a referendum on the independence of Karelia from Russia, and on its incorporation into Finland. For that, he was fined 100,000 rubles, or ~$3000.
Since then - in a twist of even more irony, it was done at the end of 2013, just before that whole Ukraine thing blew up, and Russia itself ended up arguing the separatist cause in Crimea and Donbass - that law was strengthened further, and the penalty right now is up to 5 years in prison. Based on the Karelian precedent, when I'm writing something like "Crimea is Ukrainian and is illegally occupied by Russia" - given that Russia itself considers Crimea one of its regions, and given that I am still a Russian citizen - I have just broken that law, and could, in theory, be facing the penalty. Note that this applies to anyone, not just "bloggers" under the new law.
However, given that bloggers are now required to register and provide identification, in their case violation of such laws would in fact be likely to trigger an immediate and harsh response.