Yes, all your companions except Astarion will hate you.
I don't understand how we're supposed to run an evil campaign if that's the case. When playing an evil character it would be interesting to explore options like accepting Raphael's offer (which only Astarion and surprisingly Gale approve of) or use the tadpole. Getting disapproval hinders that.
Also, you have to choose Astarion, Shadowheart, and Lae'zel for an evil campaign, but Shadowheart and Lae'zel clash all the time. It's interesting to watch, but if they won't learn to get along it will be a problem. There are supposed to be more characters in the full game so maybe we'll be able to pick party members that won't antagonize each other.
Why do people see "siding with the Absolue/using tadpole" as the only evil path?
You can side with the Grove and tell people you did it all in the name of your evil god if you are an Evil Cleric or just because killing is fun. You can agree being seen as a hero is awful with Astarion afterward. Who you side with isn't a good or evil choice, it's how you go about it that is. And helping the Grove is a big word, as you can leave it in the hand of Khaga if you play your cards right effectively corrupting it (that path is a bit bugged right now).
On top of it, a cleric/paladin, especially the evil ones, should want to sabotage/destroy the Absolute cult, not join them.
