The answer to the title is yes. It's part of his charm. I agree that the scene is creepy, but I can't help but love it. The sexy vampire is an old trope, but a successful one nonetheless. While I agree that taking blood without permission is an act that violets the other persons body and trust, Astarion found himself in a pretty desperate situation: he's too weak to hunt animals, but too scared to admit the truth to his companions, which barely know him and might just kill him for what he is.
I'm not trying to justify him - what he did was defiantly wrong on many levels - but if you haven't noticed, Astarion morals are shady at best. He's the bad boy of the group. If you want to kick him out or kill him it's your decision. One of the things that I like about this game is that any decision has сonsequences (especially if you let one of the shady people help you with the tadpole problem).
I think that a possible solution could be catching him feeding on an animal or an enemy. Another option is him collapsing on you because he's too weak from not feeding. Than it would be your decision if you want to let him feed on you, or maybe even hunting an animal for him.
