I put a lot of thought into my post, so I don't appreciate you referring to legitimate discussion as shitposting. This is the second time you have resorted to a personal attack instead of addressing arguments that disagree with you. if you can't be objective you should probably refrain from posting.
As for the rest of your post the whole checks and counters argument has become somewhat stale. I'm sure there untested sets that can defeat top tier threats. That's the very nature of 1v1. Your set only has to work once and beat one pokemon in 1v1. It doesn't have to support a team or beat more then one thing, and it doesn't have to deal with the opponent switching out. Hence a greater number of "viable" sets. I mean the Sylveon set you named loses if you Endure and Mega Salamence uses Toxic then Giga Impacts. Its unlikely to happen the first time you face your opponent, on the ladder you can face the same opponent multiple times so it could come on. Thats why i say the whole checks and counters arguments are stale. Anti-Ban posters will just come up with some set that beats some Mega Mences and Pro-Ban posters will figure out a viable way for Mence to beat the check. I seriously doubt this argument will go anywhere. Instead we should focus on Mega Salamence's own traits, such as its ridiculous stats and great abilities. I think we can come to some conclusion about whether or not Mega Salamence's own traits are significantly better then the average 1v1 pokemon's traits in a manner that makes Mega Salamence broken.