Real were forced to play with ten men after Raul Albiol's dismissal.
Ramos said: "Our attitude was good after the sending off and we did well to draw the game.
"The referee could've sent Dani Alves off when he fouled Marcelo for the penalty, but he didn't. Yet, he didn't hesitate to send [Raul] Albiol off."
Ramos added: "We are forced to keep fighting until the end because there is no mathematical champion, but it would be difficult to win the league [this season]".