Here's the situation: we have four gliders. We just got our new boy a over a month ago, so we've finished the quarantine period and have decided to introduce him to our trio. We have two girls and one intact boy (our new boy is neutered). We introduced him separately, he hit it off wonderfully with the girls (they are sweet and always loving, never had an issue with intros) but when it came to Desmond, they started fighting immediately. I wasn't surprised by this, as we had them in the bathtub so there wasn't anything he could've been too territorial about. We're currently swapping their pouches every couple days, but Desmond seems really angry every time he catches any scent of Harrison. Harrison has been staying with the girls for the last couple nights, and they love him. We put the girls in with Desmond (we initially got Harrison so Desmond would have a buddy, because he's alone in his cage) and Desmond would sniff them and start crabbing. He seemed confused because he was smelling Harrison but it was on his girls.

I think it may be a territorial thing but I'm not positive. When we got Desmond, we had a lot of bonding issues with him. It took us an extremely long time to get him a little comfortable with us. Right when he started letting us pet him and get him out of his cage, he matured. So I can't tell if he's aggressive because of his personality or because he is matured now. We're thinking about just getting him neutered and letting him heal and get all of the extra hormones out of his body... I was just wondering if this would be a good idea, or if there is anymore advice you guys have to help me keep bonding them... I'm hoping Desmond will see Harrison as one of his, and not competition!

I think having Desmond neutered is the best option to try. Sounds like you have the right idea for approach. Getting those mature male hormones out of his little body is likely to do the trick. Then, you can restart the intro prep again with a better chance of successful introduction. Also, safer for the girls.

According to your timeline you rushed the introductions and did not give enough time for ,what I call, "scent training".

you say, "We just got our new boy a over a month ago, so we've finished the quarantine period" then you introduced them.
from my readings, and the way we did it, we would swap sleeping pouches for a few weeks, then put cages 6 inches apart for a few weeks. So another month or more of time after quarantine passed, then after the gliders had time to smell the other and then see each other we would do the bathtub introductions.

Like you found out, many gliders love having other gliders around and are quick to make friends, but some are harder to be friendly. My wife has done about 5 introductions, with one female taking almost 2 days to warm up to the new additions, and another time one female was rejected by 3 colony gliders, so she had to be removed.
I suggest going back to scent training for awhile, then try again later, you can also see at night how they interact behind the cage bars.