While MC is indeed slowly losing his humanity bit by bit, I wouldn't say that what he did in this chapter is uncalled for or an act of evil of any sort. Since early on he was portrayed as someone who protects his family and loved ones, he'll do anything for them and will do anything to protect them at all costs. He clearly has said that he doesn't want his family ever involved or for any harm to come to his family. Now this idiotic Adam White dude just came to him and told him that his (as far as MC knows) "dead" dad is going to become public enemy number 1. In other words, they're going to go after his dad, and I'm sure MC has a lot of mixed feelings about his missing/supposedly dead father as well. So Adam was pretty stupid to just bring that up the way he did, he should have come at it in a much more careful manner.