That must be really conflicting for you. Sorry to hear that.So I get that he was never really nice anyway before he went mental.
My Dad was my best mate for decades, I played in bands with him from the age of 12 but 7 years before he died I found out some horrible things about him that were kept away from me.
I was ordered to be civil to him and not bring things up but also lucky I only saw him about 4 times a year for 30 minutes.
I feel guilty that I haven't cried for his death but cried for Ozzy.
I think that sometimes what triggers the crying isn't the true cause. For instance I get quite emotional seeing selfless acts of heroic behavior where people save lives etc.
We're complex animals, I would always encourage people to speak to professionals to help deal with emotions and feelings that you struggle with processing.