@JoyfulCrown Like you said, blunders happen to everyone, so everyone should have a fair chance to win a game when their opponent blunders, whether their opponent is a much higher rated player, a much lower rated player, or anything in between.
And if a lower rated player chooses to accept your seek, then you know the must want to have a chance to win. So not allowing them a chance to win kind of defeats the purpose of the entire game.
And anyways, rating is just a way to measure skill level and a guidelines to rank players according to their skill. So will a noob really learn anything from winning against a blunder? Probably not. He'll get his 10 rating points, you'll lose 10 rating points, but eventually you'll get those back, no big deal. And he will probably lose his 10 rating points and go back to whatever he was before your game.