As for the steroid argument... right now 100% of the players are on some form of dietary supplement. most are legal. some are legal now and in time will be banned. IE...Creatine was once legal and used widespread, now it is not..... for that matter caffeine is a performance enhancing drug, and a dangerous one... one day it may well be a banned substance... will that make everyone who ever used it a cheater... absolutely not... you play within the rules that you have in the era you play.
Belicheck was once a great DC. His first stint with Cleveland as a HC was less than stellar. to here dick Hoak tell it, back in the 90's when the league still shared videotape for upcoming opponents, the steelers, prepping for the same team Cleveland had just played, once received a tape from Cleveland of the next team they were playing that had their opponent's practices instead of the league gametape on it. he was retiring when he said that, and that teams knew what BB did and just didn't want to make a fuss about it.
The most telling stat was when Football outsiders, right before Spygate broke, tried to make the claim he was the greatest coach ever based on a breakdown of the best coaches of all time and how often they had the correct offense or defense called for an opponent's formation... he was near double of all the other greats... then they revisited it the year after the league instituted very curious fixes, such as spontaneously encrypting the offense's QB helmet signals and letting the D's wear mikes, his numbers suddenly dropped into place with every other very good to great coach, and, not coincidentally imo, where he was at as a DC...