do you think that this type of deception is morally fair to those persons he deceives? why or why not?

Dentes has a vendetta to settle. He was clearly wronged in a pretty bad way. In this sense he is a heroic protagonist. There would not be much of a story if Dentes didn't put on clever disguises and wasn't supremely pissed off over what happened to him. In this context, the morality of telling lies and deception are a means to an end that provide the reader suspense. So, in an escape-fiction sort of story like this, Dente's deception works well.