If they had, as LE said, a couple little weed grows on their land, then that kinda pulls the R's ability to blackmail anyone else about drugs. No one wants a felony or their weed op shut down. If someone who was doing something illegal, was trying to blackmail me and I was doing something illegal, it would be a stalemate.
ETA: However, if it was a rogue cop, that changes the game entirely.
JMO, if CR1 was only growing weed, but threatened to expose W's if they were engaged in trafficking of hard drugs, it ups the ante a great deal. The penalties for hard drugs are much heftier than for growing weed. The W's may have already threatened CR1 over his own grow op and he may have felt he had nothing to lose. W's may have been willing to pull out all the stops in order to get custody of S. It's also possible they weren't aware that CR1 knew of their other drug activities.
It seems there was something explosive that happened in the custody dispute that resulted in the W's deciding to participate in the murders of 8 Rhoden family members. It had to be something really big in that battle to trigger such drastic action. Not an impulsive act, but something set off a deliberate plan to kill them all. A decision that resulted in a time period of intense planning to carry it out. Something CR1 or others said that caused a drastic yet controlled plan to annihilate an entire family.
JMO, CR1 said or did something that crossed a line and put his family in danger and it was done in the heat of the custody battle. He may not have made a direct threat, but he stood up to the W's in a way they felt it necessary to interpret a threat or concoct one.
What was said or threatened? What else could have tipped the scales towards pre-planned mass murder of 8 family members? When LE responded to the fight on UHR a couple weeks before the murders, did CR1 make a direct or indirect threat against LE when they responded? Who called LE that night & which county responded?