Let me first to say that we all know that Patrick Jane is a actually a gay man.
We all also know that Kimball Cho is a man of love and compassion.
So...but back in the day, when Cho hadn't fully dealt with his own feelings, the now openly gay detective would target his anger toward others, specifically — gay people still in the closets.
Kimball was very angry, very rebellious and used to look at gay men and think, 'I'm not like that, I don't want to be like that, that's not me.' He was ashamed. He took his danger out on those around him and their families. So he brutally murdered Patrick's family in order to help Patrick come out from the closet.
We love you, Kimball, and we're so proud of how far you've come!