What terrified Samuel and Scarlett the most was the realization that if the Lopez family discovered Rick's illness, it could spell total disaster for the Wilson family. The once cherished Rick would be loathed by his parents, who might only refrain from hating him as long as they retained any semblance of parental love.
Samuel had already decided that they needed to have another child with Scarlett. Until then, Rita, as their only healthy offspring, was someone they couldn't afford to alienate. In fact, they were even discussing how perfect it would be if Josephine were into men—then they could hand Rick over, using him to help the Lopez family fight against the White family. That way, Rick could at least redeem himself in some way.
All their plotting was relayed to Rita through the little spider she had left in the Wilson household.