I didn't mean that you can just take other people's critiques as sound nor unbiased, but I can guarantee you that the GiveWell competitor won't share your bias.

In theory, you're even his intended audience (liking EA but not 100% convinced), which means that if he's doing his job right the arguments would be tailored to you. (Though I suspect tailoring an argument for rationalists might require different skills than tailoring it for other types of groups.)