I don't see him as pure evil because of compassion and understanding. I played with Astarion in my party multiple times and he doesn't do a single bad thing in my playthroughs nor do I have any issue getting his attitude high primarily making good decisions. Sure he has his opinions on certain matters, but that's pretty much all he does. He's pretty much harmless as long as he's with me and he's behaving himself.
If he was pure evil, then he would gut Gandrel on the spot without a moment of hesitation. He'd feed on the innocents and he'd try biting us even after saying no. But he's being a good boy instead, despite his issues. Maybe if people gave him a chance and actually took him along for a playthrough, they'd see he ain't so bad as they thought ^^
Astarion is evil, not stupid. He is trying to not get himself killed or brought back to his master. Take him and go murder or do act of cruelty and see how he enjoys doing that. He loves bloodshed and killing people. He's ultra happy after you help the Goblins wipe out the grove. He's how chaotic evil should be role-played instead of the acting stupid murderhobos too many people believe evil is supposed to act like in D&D.
Which is really the entire problem with the discussions in this thread. Way too many people think:
- evil = murdering everything that move
- good = helping people and being nice
- neutral = money, money, money
That's not how D&D define the alignments. The D&D alignment system was based off virtues. Lying fall under evil, even if you are doing it for a good cause under D&D alignment system.