.. he was the only one pointing out the hypocrisy of slaughtering the goblin village as being "good".
What hypocrisy? What *village*? It's a FOB for the Absolute's forces. The Gobbos are looking to kill the Druid Grove, eating roasted Dwarf until they do.
Its got kids there and we attack it in the middle of a party and then even on ge most bloodless path we kill the leadership to create a goblin thunderdome.
Don't get me wrong saving the grove is probably still the better option, but let's nit oat ourselves on the back too hard.
There is nothing wrong with wiping out a goblin stronghold, goblins are vile, murderous vermin that delight in cruelty and torturing those weaker than them. Sorry, but I don't buy the WotC nonsense of "they're sentient creatures and have free will".
Anyway... let's get back on topic.
Astarion is definitely evil, he delights in acts of cruelty and generally detests helping people. Resisting the book has nothing to do with it, especially as he isn't a wizard so having the book would not aid him. He'd still require the protection of a party and I have little doubt about him sacrificing anyone who lost their usefulness for him. He's an absolutely self-serving individual ... and that clearly makes him evil in D&D's context.