De la Fuente was angered by suggestions that the teenager had avoided the first Nations League fixture against the Czech Republic, insisting the decision was made on medical grounds and that the same approach would have been taken with any player.
The Spanish Football Federation confirmed that Yamal had experienced discomfort in his right knee following Barcelona's match against Atlético Madrid. He remained in Barcelona to continue his recovery rather than travel to Prague for Thursday's game, with the possibility of joining the squad ahead of Sunday's meeting with England at the Metropolitano.
Mikel Oyarzabal was also unavailable for the Czech Republic fixture because of a separate problem. However, while his absence attracted little controversy, Yamal's situation prompted speculation that he had deliberately withdrawn from the first match.
De la Fuente strongly rejected those suggestions when questioned by journalists.
"What hurts me most is the lie, the lack of rigour, the lack of truthfulness and the invention. I have explained everything because it is the only way for people to know what the reality is. I cannot stand people who try to deceive and lie," he told MARCA.
The Spain coach explained that the decision followed discussions between the national team's medical staff, Barcelona and the player. He said the priority was to avoid an unnecessary journey while Yamal continued treatment with his club.
"Lamine has inflammation in his knee. Our medical staff examined him and I decided that, to avoid this trip, I preferred him to stay at home and train with his club," De la Fuente said.
He criticised those who had drawn conclusions without knowing the medical circumstances, arguing that the decision had been taken in the player's interests rather than to give him special treatment.
The coach also made clear that Yamal's status within the squad had not influenced the decision. Although the Barcelona forward is one of Spain's most important attacking players, De la Fuente insisted that no individual receives preferential treatment.
"I am not worried about messages from outside because I am here to clarify things. People create arguments that have nothing to do with reality. Lamine has no privileges. We would have done this for any other player," he said.
The situation was being monitored closely, with De la Fuente indicating that Yamal's recovery was progressing well. He expected the forward to join the squad on Friday, leaving him in contention for the England match.
The decision reflects the importance Spain place on managing the fitness of a player who has become central to their plans. Rather than risk aggravating the problem in Prague, the coaching staff chose to give him additional time to recover in Barcelona.
De la Fuente's frustration was directed not at questions about Yamal's availability, but at the suggestion that the player had shown a lack of commitment. He was adamant that the medical explanation should put an end to the speculation.