Eto'o missed a sitter from five yards, hitting the bar with an open goal to aim at while also completely missing an attempted volley as Inter rallied late on in Sunday's Serie A clash.
They lost the game 1-0, Eto'o's misses proving costly as they slipped to eight points behind leaders AC Milan.
Inter can close that gap to five if they win away to Fiorentina on Wednesday, in a match that was postponed in December due to the nerazzurri's participation at the Club World Cup.
"It takes a brave man to criticise Eto'o, he's scored 27 goals," said Leonardo.
"It can happen that in one second he doesn't find the right space or contact but talking about an Eto'o problem that doesn't exist, I can't believe someone can get knocked down for something like that.
"It seems to me as if it's an attack against Inter, as if they (the critics) were waiting for us to lose a game."
Leonardo also insisted that the title race was not over because of that defeat.
"Everything is still open, non-one can claim to have won," he added.
"We're playing well and we're the best team in the world. I can't get involved in these dramas, either accept me as I am or leave me alone."
And an angry Leonardo hit out at the brickbats.
"Often people exagerate, I'm asking for a bit of coherence. I defend the team, talking about me won't change much," he said.
"It makes me angry to hear people talk about this team as they have been, there's no (Diego) Milito issue or Eto'o issue or an issue with anyone, I can't accept this.
"I don't intend to hide a problem, we struggled also against Palermo but look at the numbers.
"I would sign on the dotted line for seven wins in our next nine matches, I'd like to see where we will be and where the others will be."
Leonardo has won seven league games and lost just two since taking over at Inter, while also winning a pair of cup matches.
But the defeat against an otherwise struggling Juventus has seen the critics emerged from the woodwork.
And the Brazilian has been criticised for his side's leaky defence, although they have also scored a lot of goals.
"My idea of football is to always try to win while playing good football," he said.
"At home and away it's always 11 against 11, always on the same pitch, there's no influence on a team this strong.
"We just need to play and try to hurt our opponents, we don't need to play less like we know how, all we need to do is play to hurt our opponents and we have the quality to do that."