The SBL is essentially taking the position that you can only belong to the SBL if you don't believe in the Bible. Only secular scholars are allowed to be members. If, by contrast, you believe the Bible to be what it claims to be, then you can't belong to the SBL. If you believe the Bible and act on its teachings, you will be expelled from the SBL. That's the logic of their position. We'll see how far they take it.
Respecting IVP and IVCF, views held employees of a religious organization regarding homosexuality will naturally impact the editorial viewpoint of that organization in publishing, campus ministry, &c. It's quite germane to their mission.