I changed my avatar just for this.
I will play the role of Miss Martha Costello, my favorite fictional barrister, and I will be defending my client, Mr. Mega Metagross, who has been accused of being to powerful for the Ou metagame to handle. So Your Honor (aka Judge Haunter) lets us begin.
Just be wary that I prefer to prosecute, so please be mindful that I have little experience when it comes to defending.
Anyway, the prosecution argument seems quite flawed to me, and I have only seen 1 post (praise goes to Mr. Albacore) on the ban side of the argument that truly has good justification and reasoning for why mega Metagross should been banned.
Anyway, on to the arguments of why Mega Metagross "should be banned
1. It has no checks/counters!!!
Incorrect. It has checks, depending on what move it runs. Which comes to the problem. Mega Metagross can hit every pokemon for super effective damage, however, it cannot do so all in one moveset. I am not going to call it the 4MSS, but it is a form of which the pokemon has no safe switch ins, but at the same time, it does. For example, counter skarmory is a safe switch-in if Metagross lacks thunder punch. Slowbro and it's mega form are both safe switch-ins if Metagross lacks grass knot. Landerus Therian is a safe switchin if metagross lacks ice punch. Similar to Greninja, who could "pick" what checks it, Metagross can pick the moves it wants to deal with the pokemon that may threaten the team. The difference is that Metagross's counters have other uses then just checking Metagross, unlike Greninja, who's counters were pretty much only used so the team would not get dismantled. Anyway, while mega Metagross does force a Guessing game for what moves it has, all it's check can take a hit, even from a powerful super effective tough claws boosted one. This means the team will pretty much know Metagrossess moveset, so they no what to expect for future encounters during the same battle. Also, just becuase a pokemon "has no counters" does not mean it's broken. During BW2, Hydreigon was pretty much uncounterable, yet it was not broken. Also, max Defense mega Sableye always checks Metagross when healthy, not matter the movset.
2. It's base stat total is too high!!!
So? Kyreum B has a higher base stat total, and it's not broken. Mega Diance has a similar layout of stats, and it's not broken. This argument is completely invalid. Just becuase a pokemon has amazing stats does not mean it's broken. I am going to leave it as this, as this is pretty self explanatory, but you really should not be judging a pokemon by stats when it comes to suspect testing. I know Metagross has perks over Diance and kyreum, but I think that just saying that somethings broken becuase it's stats are high is lazy and invalid.
3. It destroys offence!!!
Okay... Yes, as far as switch ins on offensive teams go, mega metagrioss has next to none. However, it can be reveng killed by the most popular offensive pokemon, bisharp, with relative ease. Other fast mons such as raikou, starmie, choice scarf excadrill, choice scarf landerus, Talonflame, choice scarf gengar, mega Manentric and mega loppuny, with some prior damage. The catch is, that mega Metagross will almost always have some. One point that I feel has been strongly overlooked by the prosecution is that Metagross has to take a turn to mega evolve. Mega Metagrossess base form is quite vulnerable, as it has only average defensive typing, and low speed, meaning that against offence, it is pretty much forced to take hit, which normally leaves it around half health, making it an easy target for stuff like bisharp to come in and finish the job. Also, it sits at a crowed speed tier, which is actually not beneficial, as it ends up taking a ton damage for most of the pokemon that speed tie with it (gengar flat out OKOS, Gallade does a ton of damage, Latios equakes or hp fires.) Overall, while Metagross seems broken at first, with a combination of speed, power and bulk. However, when you look deeper, mega Metagross is much more vulnerable then you may think. It always looses to something, so it's no uncountrable. It is vulnerable the turn it megas, and gets outpaced an revenge kill by quite a lot of notable threats. Finally, and I leave this open until the suspect ladder comes out, it may in fact hold then metagame together. I hope my client is given a fair trial, and Your Honour please note these facts. Let's give Mr. Mega Metagross a chance to prove his innocent. He may come in later himself to prove it.
In conclusion, DO NOT BAN MEGA METAGROSS TO THE UBERS TIER.