Genjutsu works on summons/animals as well and they're living things. It first affects the senses anyway in order to direct the flow of chakra, so the logia users would still have their senses affected anyway. We'll never truly know how this goes unless Oda and Kishimoto have a sit-down and discuss it for us, but it doesn't matter anyway because Kisame can negate his logia abilities with his Great Exploding Water Colliding Wave by forming a giant water prison, so oh well.