I can see his logic- if he had TJ with QK on the board, any 9 or A would have given him a straight, I see people call with an open end straight draw all the times especially with two cards to come. It was a bad beat that he got JJ to match his J, but any A or 9 would have just been hitting his draw. I don't know what the value of the bet and pot is so can't comment on pot odds (and chances are he/she had no idea about these odds either), but it might not actually be as bad a call as it sounds.