I understand your explanation Policy, but from what you said in game it seems that you were lynching him because you were mad at him, which is considered grudge lynching. In the future lynch the people who you think are mafia.
I play a game of probabilities. I know most people here don't realize Mafia is probabilities, but it is.
The two remaining players were, at first glance, 50/50 likely to be mafia; however, if you look at Hibiki's play day 2, he forced the PR to out and reduced the win probability of town. This increased the probability that he was mafia, and therefore I was forced to vote for him.