ML hid that blondie and protected him when he was a wanted person. Years later when his brother came into power, rather than escape with the ML and go into hiding he chose to stay and aid his brother. The man who was actively seeking ML to kill him. Same dude that killed ML’s father and brother. He said he joined him in order to protect him but ML would have been fine running away all together with him.
Then you’ve got the rapist guy going on to snitch where ML was located out of revenge against the blonde dude. Yeah Blondie sent a letter to tell ML telling him to run but then when they arrived to go kill him, when given the choice to spare or kill the people who were supposed to be friends/family, he said to kill them. “He did it to help ML”, he clearly didn’t know ML well enough if he thought killing them was a good choice. Which is especially shown when ML rages on the memory saying he would have rather sacrificed himself than allow his friends/teachers to perish the way they did.
Yeah there is a chance of one of them saying where he went but you also have to take into consideration that ML could have just kept running away/hiding. I doubt he was gonna stay in one spot for very long. So the blondie not trying to stop the killing of a bunch of innocent people was absolutely insane. These people took him in, they cared for him along side ML and he betrayed them.
Then you’ve got him wanting to harm/kill MC, yeah he’s in pain from not having his blood sucked for years but when it comes down to it he showed he hasn’t really changed, he’s very much willing to harm anyone as long as he gets his way. So idk where you get he hasn’t done anything wrong from.

AHHHHHHHHHHHHHH ARE YOU KIDDING ME?!?! THE WHITE HAIRED DUDE DIDNT EVEN DO ANYTHING WRONG WTF ARE YOU TORTURING HIM FOR?!?! ISTG AT THIS POINT THE ONLY REASON IM READING THIS FOR IS FOR SOOIN AND JOOHYUN