From the 1979 interview, as cited on Wiki: >Before Serpico, you were up for Best Supporting Actor for The Godfather. Do you feel you were in the wrong category?

>Pacino: Oh, sure. Definitely. That was outrageous. It's things like that that get you a little sour. I decided to pass the ceremonies by. There were certain people around me who wanted to write a letter, who wanted me to announce that I would not accept the nomination. I would always say, "Let it go. Let it go. Don't make waves." But then, even though I didn't go, I watched it on TV. I felt bad. I didn't care for that kind of contradiction.

Sounds like he was encouraged to boycott it but didn't follow through on an official level. He just didn't show up. That could be taken as a statement in itself, but he wasn't one for public appearances or doing a lot of press, so it probably didn't even register with those not in the know as a rebuff. And then he felt bad, haha.

Edited to close the quotation marks