Despite releasing a video over the weekend where he stated his desire to represent England in all forms of cricket, Pietersen has been dropped from the Test squad that will take on South Africa at Lord's later this week.
News of Pietersen's omission has come following allegations that he had sent text messages to some of the South African squad, in which he verbally attacked some of his England teammates.
However, Warne believes that a player of Pietersen's talent should be included in the squad, regardless of the ongoing situation.
"If KP didn't play second test V SA the score line would read SA 2 ENG 0.. SA ranked number 1 test team in the world, need I say more," Warne wrote on Twitter. "For English cricket to be in this situation after so much good work, there's only one way now for our friendly English buddies and that's unfortunately down the rankings. It's hard to work out how it has got this bad. Management and leadership has to be looked at.
"When someone is gone you realise how important they are to you and a team. In this case, how much you miss them and their character.
"It's more important to be respected than liked in a team environment. For that matter in life, only way you get respect - earn it.
"So, if the England players have lost respect for KP and KP them - its irrelevant whether they like him or not. I didn't like some players! And for that matter some didnt like me, but once we stepped out n the field - unit !!"
Warne and Pietersen were previously teammates at Hampshire.