This is a derogatory term for left leaning people who have naive, unrealistic, and overly optimistic views about how the world works based on what they would like to be true rather than what is actually true in reality. How the leftoid would like the world to work is usually based on dogmatic ideologies like feminism.
There is an emphasis on them being biology, genetics, and evolution deniers. Leftoids don’t explicitly deny evolution in all of its forms like the religious right. They only deny evolution and biology in special cases where facts conflict with their ideologically motivated beliefs. Especially with regards to gender and race politics.