@Fujishiro
This chapter also does confirm that anyone who makes a deal with Imu also becomes brainwashed by Imu, as shown by Dorry and Brogy now being on Imu's side.
Which also explains Gunko having that flashback about Brook in the previous chapter.
But at the same time, I don't believe they all become brainwashed by Imu after making a deal with him.
I highly doubt the Five Elders, the Figarlands, and Sommers were brainwashed after making a deal with Imu.
Those guys I'm pretty sure were already evil bastards way before making their deal.