I voted yes but this is such a hard decision, I'm definitely conflicted. Trying to be neutral as a ROB player is tough, but if it helps make me seem less bias, metaknight is already banned in my region.
Firstly, I'd like to say that that foremost, this should be a decision made based on whether or not this improves the community as a whole, and secondly, one based on balanced. Why? If there wasn't any negative impact on the community for banning him, it would be an easy decision. To put it another way, let's say he was the WORST character, but greatly negatively impacted the community; in my opinion, depending on the impact, he would STILL be ban worthy, regardless of whether or not this is a realistic scenario. As a small aside, much of my argument also applies to standing infinites, and melee players constant bashing of brawl. All these do is negatively impact the community, with no real gain.
On the plus side, without metaknight, a much wider array of characters is possible to compete with. I know metaknight isn't every characters worst matchup, but when 30% of the tournament is metaknight, the one or two ddd's at the tournament that can infinite you are more of a back thought. Many people go to tournaments knowing full well that even if they played exceptionally that day, they would run into a metaknight eventually that would prevent them from winning, it's more of a question of when, and it simply doesn't have to be this way.
On the downside, you alienate metaknight mains. Many of them didn't pick up the character because they thought/knew it was the best character but because they liked him from previous games or liked that offensive play was possible with him. Regardless of their intentions for playing him, many have spent an incredible amount of time learning to play with him, and it isn't fair to simply erase all of that time spent by banning their character. The simple fact is, this is a very decent chunk of the community, and regardless of their understandable bias towards their character, their opinions on this matter a lot.
To be clear, metaknight mains leaving the game because their favorite character is banned is a huge negative to the community as whole whereas metaknight mains branching out and picking up other characters is a huge plus. The game will still be dominated by mostly top/high tiers, to be sure, but the variety of matches, especially going into finals, will be much more varied. With ally on the scene, we've been lucky to avoid seeing many major tournament having every "finals" match be metaknight dittos, but this is only a small consolation in the big scheme of things.
People constantly say that we should wait because the meta game has not fully developed, and I would agree that it hasn't, but I think the longer we wait, no matter the decision, the less fair it is to everyone. Metaknights will spend more time practicing their character, and others will stick with their favorite character without taking up one of the several characters that they can get a nearly even matchup with. So, a decision would best be made sooner than later. This isn't to say it could never be reversed or discussed again, because that is almost inevitable.
There are a few potential community impacts I didn't go into detail with, such as people who don't want him banned simply because they think banning things from competitive games is wrong and draw the line at banning characters, but at this point, I'm doubtful of how many of these people would leave the community in the long run because of this decision. Finally, some worry about the community "splitting" over this, but in my opinion, it already has, and only a decision will unify us.
TLDR: Ultimately, what pushed me to vote yes is that I believe the community will be positively impacted in the long run.
One final note is that having just the SBR vote on this isn't sufficient to get a fair result. To explain, many SBR members are taken based on tournament participation and results, in which case metaknight has a natural advantage to have more members than most other characters. It's also only 60~ people, a small minority. Statistically, the accuracy of this vote would likely be heavily skewed by too little data, even if each vote is very informed.
Having the community as a whole decide is infinitely worse though. Many people voting don't play brawl competitively, don't care whether he is banned, don't play brawl at all, or make alternate accounts to skew results.
The best option here is to have many people vote, but not have it open to the general populous. Taking state power ranking, character specific power rankings would be a good start. Taking any average or better tournament player would be even better. This would be a huge undertaking to even arrange such a vote, but I think it would be the best option to get an idea of what would really be best for the community. How to interpret the results is even a bigger undertaking, a simple majority might not suffice.