Jane: According to an article in this newsmagazine, children' s hand-eye coordination suffers when they spend a great amount of time watching television  Ttherefore, we must restrict the amount of time Jacqueline and Mildred are allowed to watch television  Alan: Rubbish  The article says that only children under three are affected in that way  Jacqueline is ten and Mildred is eight
Ttherefore, we need not restrict their television viewing
It confuses undermining an argument in support of a given conclusion with showing that the conclusion itself is false.