God, I know you're probably expecting a sexy answer but the first thing that jumped to my mind was Frank bringing Matt 'gifts'. Leaving criminals beaten up on the church's doorstep, giving them a chance to repent for their sins.

Though it's more likely Matt would try to convince Frank to stop killing and Frank refusing to, as always. Eventually Matt learns to let it go, because last time they argued about it Frank disappeared for two weeks and was literally starving by the time he came back. Matt had to stay in bed for two days drinking lots of fluids and eating foods with a high iron content.