I don't think the revelation about Sue ruins her character at all. I think it shows despite her ornery disposition, despotism, and extreme conservatism, she has a heart. It may be reserved for a very, very few in her life (she did get involved in dating the male anchor at her station for a while, but that stopped when Sue caught him with other women), but it's there, and it helps to make her one step removed from the stereotypical female Simon Legree she's been pretty much since the series started. Doing shows like last night's begins to add some shadings to the colors of many of the characters (Puck became more appealing, Artie finally had a moment, Kurt sacrificed his diva moment for his dad's sake) that *I* found very appealing.
But the show isn't for everyone and never will be.