Best advice I have is to just ignore him while remaining vigilant. But Loki has people here to help him through the things he knows he'll be doing back home. His mother is here, Thor is here, Lewis is back...
I never liked Garrett. Always seemed like a pompous ass And what? It's not hard for me to accept? I spent about the first year here trying to deal with what Loki made me do and the fact that the Loki here wasn't the same man. We can't just go punishing people for future crimes. Even if we know they'll do them. That makes us no better than they are.
But be wary and on your guard, I'm not saying you shouldn't be but, like you said, don't be the aggressor. Frigga will probably kick your ass if you do anything unprovoked.
I'm just glad Coulson hasn't popped in yet. Because I probably wouldn't even stop him from shooting Loki