To make it clear to you I don't see anybody on the left, even the so called regressive left you talk about have much positive to say about the Middle East or many practices that happen their due to their religion. In general people who feel the "regressive left" has a positive view of the Middle East are making assumptions that the fact they don't say anything negative about the Middle East when defending the individual right of a Muslim person to exist in this society, that is somehow proof they are pro Muslim
Maybe I could have worded it better but it basically means when the left is arguing about one thing(generally individual rights as a whole or the right of an individual to live in society without somebody stepping all over their rights), the right is arguing something else(generally Muslim practices in the Middle East as if they are one single minded group of people) so the right will look at the left saying something good about the individual as somehow supporting every single thing in the Muslim world.