How are the All-State selections made? I can't speak for the other Divisions but here is how it was done at 1A. At a meeting of the coaches (not all teams were represented) a list of quality players was created. Based on the schools ranking, or perceived ranking, they were allotted a number of spots on the team. Thus you see Christ Church with more spots than anyone else. Next the coaches discuss the merits of each player and which player(s) would best represent their school. Finally, the team is compiled ensuring there are the right proportion of players in each position (you know, not 16 strikers or 5 keepers, etc.).
There could be arguments to promote other methods. One could say that since Christ Church is so powerful their whole team should be All-State. One could say that each 1A team should have a representative. Needless to say, since very little intra-region 1A play exists it is hard for more than one or two coaches to have seen very many of the players. Its hard to say a defender on one school is better than a defender on another school when no one person has seen them both play. The intent was to reward the best players for the teams, across the whole state (All-State). Not necessarily the 18 best players in the state. That would be a very subjective effort - sorta like All-Star balloting in Baseball. To make it better make sure your coaches go to the meeting.
As far as a defender getting selected from a team that lost 15 - 0, consider the opponent and consider that perhaps the reason they lost 15 - 0 was because that defender wasn't there, or maybe not at 100%. Whatever the case was, the coaches at the meeting felt that this player deserved recognition for his play.
I hope this helps.