see other sources

A quick look at other sources suggests that the real problem here may be a mother who can't take a joke.

It appears that this teacher is quite popular with the kids and regularly calls kids "loser" in a joking manner. Most or all of the children understand that he is joking and doesn't really mean it.

While it doesn't seem like such a great joke to me, I recall a time when adults tried to be sensitive and called every kid "special", even though it was obvious to every kid that "special" wasn't so great if it also applied to every retarded kid. "Special" became an insult. This may simply be the reverse.

It's possible that the girl didn't get the joke either - I haven't seen any information on that - but it's also possible this girl is cringing every time her mother speaks up to "defend" her.

In any case, this does not appear to be as clear cut as the original link suggested.