Just what is it with Hollywood and the movie industry these days that has to make stereotypical jokes? The Avengers isn't quite a comedy movie, but it does have its moments. The scene where Hulk slams Loki into the ground multiple times pretty much killed the entire theatre. I kinda expected to see people rolling down the stairs/aisles.
The subject of adoption over the years has been a serious one. Nothing funny about it. Those who were adopted were essentially given a second chance at life. Adoptees are not bad people. It's more of sociological and environmental issues that can shape a person's life.
Thor's flippant "He's adopted" comment could easily be better. Most likely a better line would have been "He's my brother, though he was adopted and his background was from those who are worse than us." Shows his love, but also his distaste for Loki's actions. Probably would have taken all of a minute to deliver that line. For those who have or haven't seen the Thor movie, that's still a good and neutral line.
We know children, in all their innocent wonder, can easily translate this into thinking that they're bad. In the Change.org petition, Marvel Comics: Marvel Comics - Apologize to Adoption Community!, Jamie made mention of children thinking just this.
One blog claims that Jamie's asking for a boycott. Not quite. If one reads the title carefully, it says "Marvel Comics: Marvel Comics - Apologize to Adoption Community!" Nowhere in the text does it have the word boycott. Just the word apologize. Big difference in definitions.
Adopted people aren't bad. They've just been given a second chance at life when the birth parents can't or won't take care of them for various reasons. My birthmom had her reason, and that one I can understand and don't blame her for putting me up for adoption.