be down on (someone or something)
To have or express negative or overly critical feelings toward someone or something. I don't know why you're so down on Robert, he's such a nice guy to everyone! Don't be so down on this vacation to your grandparents' farm. I know it's not very exotic, but we'll still have a great time!
*down on someone or something
against someone or something. (*Typically: be ~;get ~.) You've been down on us all lately. I'm down on computers lately. Everyone sure got down on fast food.
down on
Hostile or negative toward, ill-disposed to. For example, All the reviewers were down on this play, or Ever since he was injured, he's been down on skiing. [Mid-1800s] Also see down on one's luck.
have a (or be) down on
disapprove of; feel hostile or antagonistic towards. informal