The Spain international stood on the ankles of Emre Can and Martin Skrtel during the Premier League leaders' 1-0 victory at Stamford Bridge on Tuesday - which ensured they progressed to the final 2-1 on aggregate.
Sky Sports pundit Jamie Redknapp said Costa should have been shown a red card for the incident involving Can and Liverpool boss Brendan Rodgers felt the former Atletico Madrid man was "very fortunate" not to be dismissed.
Mourinho saw it differently, though, as he felt Costa did not intend to make contact.
He said: "I don't know what you understand by a stamp.
"Maybe you are already influenced by the campaign on the television with certain pundits saying that Costa has crimes - they must be nuts, the guy who says that.
"Sky call it a crime. I have to say that he goes for the ball, he chases it, the opponent [Can] goes to the floor and he puts his foot there when he is looking at the ball... What you call stamps, and Sky calls crimes, I have to say accidental."
Branislav Ivanovic struck four minutes into extra-time to send Chelsea through.
