The phrase "down on" typically means having a negative attitude towards someone or something. There are several synonyms that can be used to convey a similar meaning. For instance, "disapproving of" suggests being critical or expressing dissatisfaction with someone or something. Another option is "dissatisfied with," which implies being unhappy or displeased with someone or something. "Disparaging about" suggests making negative comments or criticism about someone or something. Meanwhile, "critical of" expresses a judgmental opinion, often with the intention of pointing out flaws or faults. Overall, these synonyms provide alternative ways of conveying a similar negative sentiment to "down on".