Your issue all revolves around the Bloodsail Buccaneers.
It’s been a long time since i did Insane in the Membrane, but basicly the Bloodsail Buccaneers (Faction) hate the Steamweedle Cartel (those 4 reps you mentioned) and vice-versa. You kill a Bloodsail pirate and you lose rep with Bloodsails and gain rep with the Steamweedle, likewise, you kill a Steamweedle goblin and gain/lose rep the other way around.
So since Insane requires all those reputations to have been exalted at one point, you have to make a choice* about which order to do them in.
Since both possibilities result in the Insane-achievement, but 1 of the 2 results in 4 Steamweedle factions exalted, and 1 Buccaneer faction Hated, that is the route most people take (i did atleast).
Evidently you went the other way around, and thus ended up Hated with the 4 Steamweedle factions, and presumably, exalted with the Buccaneers.
Flipping it around is quite easy, just go kill pirates in Tanaris again, as you likely did before, you’ll be Hated with the Buccaneers and Exalted with the Steamweedle at some point. Or check an Insane-related guide for more specific details.
If i’m right about you currently being Exalted with the Buccaneers, i would recommend you make sure you buy all the rewards from them before you destroy your rep with them, i seem to remember they sold like a unique pirate or captains hat or w/e.
Note: i said above that you basicly have to choose between Bloodsail or Steamweedle, there are technically ways to get all 5 Factions exalted at the same time, but i think they require some seriously crazy time investment, even by the standards of people that are already Insane in the Membrane like us. I’d check out an Insane in the Membrane guide on Wowhead if i were you if you want the details on that (or anything else i hinted at).
Oh and another note: Don’t consider that getting all 5 exalted (instead of just 4 Exalted, 1 Hated) thing just to get closer to the “100 Exalted”-achievement, there are almost certainly easier gaps to fill in your “Rep Collection”