The phrase "was down on" refers to a negative or critical attitude towards someone or something. There are several synonyms that can be used in place of this phrase, such as disapproving of, pessimistic about, critical of, negative towards, and disparaging of. These terms convey a sense of judgmental or unfavorable views towards individuals, ideas, or actions. It's important to choose the right synonym depending on the context and the intensity of the attitude being expressed. Adjectives such as disdainful, contemptuous, or scornful can also be applied to describe a negative attitude towards something or someone.