That being said, if he can be attacked on first meeting, we should be able to attack all companions on first meeting. I'm not using this as a counter argument, just in case it's not clear. I'm advocating for more choices during those encounters (even if I would never kill one of them on sight ^^).
I just wanted to point out that we can already attack Gale when we first meet him, and all he does is appears. Astarian blatantly attacks us and puts a knife to our throat.