The phrase "unfair criticism" refers to negative comments or judgments about someone or something that are not justified or reasonable. It means that the criticism is not fair or true. Full definition
Learning how to deal with crushing, unfair criticism needs to be part of your skill set. (annerallen.com)
However, it's a slightly unfair criticism as this isn't a behind the scenes book. (wolfsgamingblog.com)
There has been a lot of unfair criticism of Theo of recent, in my opinion, but his proven productivity when on form and especially his performances in the big games — Theo does well in the big games — justifies Wenger's continued faith in him. (justarsenal.com)