DeNiro's acting doesn't change based on his political comments outside of acting. Awards shows are not for the fans; they are to recognize and award actors for their work. It is for them, the creatives. It is their opportunity to say things outside of their acting.
I am someone who likes to immerse himself into the characters and plot of a film. The more an actor becomes well known, outspoken, or overexposed (Samuel L Jackson, for example), the more difficulty I have accepting the actor's film characters.
I often prefer foreign films because I usually don't know any of the actors and it makes it easier for me to accept them in their roles. Thats just me.
With De Niro, I remember a film he did titled
The Intern. Cute little film with Anne Hathaway where De Niro played a septuagenarian who. after the death of his wife, decides to go back to work as an intern. I just couldn't get my mind into his character. All I saw was the angry actor I had seen on the awards show. It's not that I disliked his politics, I just couldn't accept him in the role of a meek, lovable old widower.
I believe this often happens. You might remember George Reeves. He successfully played Superman on TV in the '50s. As a kid at the time, I only saw him as Superman.
Reeves hated the part and couldn't wait to play more sophistacated roles. When he got the chance, his career was ruined. When he entered for his first dramatic movie scene, the kids in the audience stood up and started yelling, "Superman! Superman!"
