Back on the lines usage in Thor; I thought the jokes punch line was that Thor was trying to defend his brother, then whats-his-face brought up the fact that Loki had killed 80 people in 2 days. Outwitted, Thor then defends himself by bringing up the fact that Loki was adopted and not his actual brother; thus reminded everyone that him and Loki have nothing in common, just so Thor can justify the fact that his brother is a murderer.
If it was trying to offend adopted kids, don't you think they would've made a more offensive joke?
BTW, Loki's dad wasn't even dead, he was juts saved by Odin from becoming an Ice giant