Let's break this down. "farm" doesn't belong to any one person. "farm" belongs to the team and no one is entitled to any particular cs. Yes, it is best to let the carries take cs and taking cs away from carries will result in a greater chance to lose the game. However, taking cs is NOT a punishable offense nor is it a reportable offense. Roaming support is also not a punishable offense and you did not mention that he is afk from the game (just roaming). If the adc start to flame the support, do you really expect him to stay in lane?
From everything you described what the velkoz did, he was not feeding, he was not flaming, he was not afk. What he did might be detriment to the team, but it is not reportable or punishable. I want to question which comes first, you flame him for taking a few cs and then he decided to not lane with a toxic adc and roam or is it the other way around?
What you did (flaming), however, is 100% reportable and punishment. What the velkoz did was NOT worse than what you he did. Of course he will not be punished...
I don't know the full story and I only have your side of the story, but I've seen many times the toxic adc flame the support for taking a few cs and kills and then expect the support to continue to stay in lane with the toxic adc and support him.....life doesn't work that way.