Antonyms for the phrase "speaks up for" include "opposes," "neglects," "ignores," "disagrees with," "criticizes," and "condemns." When someone speaks up for something or someone, they defend or support them. Opposing, neglecting, ignoring, or criticizing, on the other hand, indicate a lack of support or even active opposition. Disagreeing with something or someone suggests a difference of opinion, while condemning something indicates strong disapproval. It is important to note that there is a significant difference between speaking up for something and speaking out against something, as one is focused on support while the other is focused on opposition.