What part of blood father vs attorney you don't even like isn't making sense here lol
What part of "snitching is snitching" isn't making sense here?
Tommy is a murderous sociopath that's taken anybody down if they got in his way. Considering the timeline of the show, he barely knew Teresi this long to have some deep emotional connection with him. Blood doesn't mean shyt. He choked his girlfriend and ended up killing her after finding out she set Ghost up to die. He was about to shoot Keisha in the middle of their conversation when she told him to snitch and thought about flipping. He finds out his father is a criminal informant, then decides to go after his best friend because he thinks he was manipulated into doing something he does without any emotional attachment 90% of the time.
At least Holly was around for a couple seasons so when she died, it mattered. Tommy found out Teresi was his father, welcomed him home from prison, built a relationship with him, found out he was a snitch, and killed him in nowhere near that amount of time. But he was blood so that's different.