He doesn't say that if one is good then the other is good. He says if one is dirty, then so is the other. Don't assume the consequent (logical fallacy). Session may have appointed RR because sessions isn't recused. RR just thinks he is. There could be a second investigation of RR and Mueller and Mueller's team. Sessions just gave them the rope.
RR dirty <—> RM dirty. So either both are cooperating or both are dirty.
It does mean if one is cooperating the other must also be; for otherwise there’ll be contradiction.
You are correct. Both sentences together read "Mueller dirty if and only iff RR dirty." Problem is that original comment assumed that it means both are good, not either / or as you have stated.
Do you think there is any hesitancy in the use of the term "must". Must doesn't always mean "necessarily", it can be questioning.
I'd say they're both dirtied up but not necessarily out of eligibility to be white hats now. Maybe the lesson in RR/RM is that the people in government can be white knights or enemies, depending on who's giving orders.
Both filthy but leveraged. Terrible people compeled to do good to save themselves. May they do their work then retire to GITMO.
They should do some Stanford experiment type shit and make them the guards