Most of the arguments have already been gone over at this point in the thread. Although, hopefully, more discussion can help sway potential voter's opinion one way or the other.
I've watched a good number of Aegislash games on the ladder, and some of the posts in this thread have been saying how Lopunny becomes difficult to counter in this meta when paired with Aegislash, how it just devolves the game to Lati, Keldeo, Lando I, Bisharp, and Aegislash being extremely common, and a large portion of OU becomes much less viable with Aegislash around.
I can say, from my perspective, although the meta usually has a small number of mons that are very common anyway, this is all correct. Now, some things I'm never gonna do are give you up, say that Aegislash should be banned because I want to use a certain pokemon, or say that because another pokemon becomes broken with Aegi around, that we should keep Aegi banned. As for the last point, the main pokemon I'll be looking at when explaining what I think is a more rational argument is Lopunny in this post.
Really, an argument that may convince some from the unban side is that because Aegislash reduces the number of pokemon in OU, that it alleviates matchup issues, and that this is good for the meta. While it is true that Aegislash does reduce the number of pokemon in OU, I certainly do not agree that it prevents matchup issues. People initially thought that this was the case because it reduces the number of threats, but I for one did not consider the possibility that it also dramatically limits the responses to those threats. While Metagross and Diancie might have gone down in terms of effectiveness, threats like Lopunny now have few switch-ins to beat them; I'm much more reluctant to use Clefable or Slowbro to take on Lopunny now that Aegislash is around. I'm not going to claim that Lopunny is over-centralising because of this, because it does have some switch-ins, but it does mean that many teams that aren't built right from the get-go with it in mind will be weak to it, and so will suffer from exactly what bringing Aegislash down would try to prevent: A bad matchup.
As for Aegislash itself, it's undeniably a very good pokemon despite players trying to prepare for it as best they can. That being said, I'm very aware that it isn't sweeping teams by itself. As to what it does, that's really another matter, because it can really do whatever you want. If you need something to chip away at defensive stuff like Hippowdon with Toxic damage racking up, it can. If you need something to break teams apart with very strong coverage and hard-hitting moves, giving it very few switch-ins, it can. Although I'm personally not a fan of it, the SD set to clean up is also an option. Obviously, all of these sets will fill the function of checking a large number of mons, and being a good switch-in to stuff like Lati. The issue with this is that it just takes splashable to another level. Some might say that certain pokemon become used again and again anyway, and that it isn't a bad decision to add another pokemon that just becomes one of those. The key difference between Aegislash, and very common pokemon, like, for example, Latios or Keldeo, is that when you used the latter two, you have some idea of the qualities you want from them, and how your team can benefit from them before you put them on a team. A Keldeo check with hazard removal is understandably an in-demand role, as is a scald-spamming Bish check. However, you can safely put Aegislash on your team before deciding what set benefits you the most, because considering all of the possibilities it brings to the table, there's really very little reason not to.
It doesn't even need to be stated that while 50/50s are present in the game anyway, Aegislash forces excessive 50/50s, and it isn't too uncommon for games to be decided by whether the opponent uses KS or not. Hopefully, suspect voters can agree that a metagame where 50/50s are not overly excessive is preferable to a metagame where 50/50s are, and see that this is yet another reason to keep Aegislash in Ubers. As for the KS ban, Aegislash has sets, mainly the All out attacker one, that are still very effective without it. If it doesn't contribute to the meta by alleviating matchup issues, and dramatically limits options in building, there is still no reason to bring it down. Furthermore, it's been mentioned that this is an irritating halfway house choice, Blaze Blaziken isn't legal anywhere but Ubers, neither is Torrent Greninja, therefore neither should KS-less Aegislash, and this is a point that I wholeheartedly agree with.
Overall, the metagame has essentially changed from something which, while it may be messy, it is at least somewhat diverse, into Aegi with a good number of Aegi checks while using as little stuff that loses to it as possible, only real exceptions that come to mind being the Latis. Personally, just from my own teambuilding perspective and how limited my options are in how I can choose to piece something together, that really just results in a stagnant game that will only get more and more dull over time. In conclusion, I urge people not to vote unban because they are dissatisfied with the current metagame, a much more sensible approach seems to be to suspect more pokemon currently in OU rather than let another back in, and to keep this highly splashable, 50/50 causing, metagame stagnating threat in Ubers where it belongs.