On reflecting on the revelations about INRA to the galaxy at large, my own judgement would be that INRA was once a vital organization for human defence which suffered a tragic failure of conscience. Whatever our struggles with Thargoids, then or now, genocide can never be a viable solution. If nothing else, it removes our right to protest if and when another species decides to wipe us out for their own safety.
That said, as with Vasious, I find no real justice in killing a descendant of someone who worked for INRA. It's a most peculiar, if not stupid, form of revenge. Even if INRA had a role in killing Mic Turner, I would think the better solution would be to find the killer in question and put them on public trial. Ditto with the people who ordered the use of the mycoid virus... though with our current war, I doubt a fair trial could ever be arranged, one way or another. Justice for Turner and the Thargoids will have to wait until our current war is over.
Personally, I think the links between the Senator's assasination and this LoR to be a little too pat for my tastes. For one thing, a secret organization that has tasked itself with wiping out INRA would not show it's hand so quickly by leaving such an obvious note behind. Now the alarm is raised, any any future assassins would find their quarries harder to get at. But the resulting struggles and deaths might serve another purpose - muddying the search for who really wanted the Senator dead.
After all, it's more likely the late Senator had more contemporary concerns and more enemies in the present day, many who are probably quietly celebrating his demise. Finding the Senator's link to INRA - and pairing that up with people who probably would want to kill him for that link - would be quite an opportunity for those enemies. The League of Reparation thus becomes their pawn, and any other INRA descendants (and LoR members) killed later on become collateral damage. If I was the Imperial investigator, I'd be prying into the late Senator's current business, and seeing who benefits most from his death.