I don't see any reason to hate Charlton or disrespect his memory for several reasons, but one main one is ever more prudent; we've won.
United are seen as secondary to City in every current clash. We've won multiple Premier League titles, we've won them back-to-back, we've won three in a row and chasing a fourth. We've won the FA Cup, League Cup, once four years running. We've won the pinnacle of European Football and most importantly, we've matched their highest achievement, what that club dined out on for years as the highest accolade not even Liverpool, Chelsea or Arsenal have acheived or anyone thought possible, The Treble.
Charlton saw it all. He saw us rise and his own club fail. He saw the dilapidated, crumbling Old Trafford looking worse now than when the Germans bombed it. So there's no need to insult his memory further, City have already regained our pride for us where it mattered, on the pitch. Any and every comment he may have made about our club have been well and truly silenced. So I do hope any Blues going to the 'Colander' to reflect that pride back at them. Let them have their respectful moment of reflection for a past player who saw successes at their club... and observed ours.