No, it's unfairness that was getting the Empire and Clan cultivators killed. Matt calling for fairness seems to have stopped most of the infighting (aside from the death squads that were specifically sent in to kill powerful Pathers and seem to be from other Courts), but it didn't make the Federation and Sect cultivators act to support the Empire and Clan cultivators instead.
There are probably thousands of Federation and Sect cultivators just in the Winter Court. Trying to kill them all will just get Matt's party swamped and killed, and the neutral forces will feel threatened if they somehow managed to succeed. Right now, Matt is just trying to get this floor over with as quickly as possible, and that means getting the Federation and Sect cultivators to at least stop sabotaging their allies long enough to finish the floor.
If it helps, I'm pretty sure that a lot of these cultivators are going to end up dead once the floor ends. I've been envisioning them crowding in to swarm Matt, and then he uses whatever beefed-up version of Sword Rain he came up with since the Tier-10 tournament.