You have to read the article to see the context in which Johnson said it, talking about liberals' opposition to school choice in D.C. Read what he actually said:
It's unbelievable to me that liberals, that President Obama, of course he sends his children to private school, as did Al Gore and Bill Clinton and every other celebrated liberal. They just don't want to let those idiot inner-city kids that they purport to be so supportive of, they want to help out, they don't want to give them the same opportunity their own kids have. It's disgraceful.An infelicitous choice of words to be sure, but it's clear Sen. Johnson actually meant that Obama, Gore, and Clinton act as though they view inner city kids as idiots upon whom school choice would be wasted. Favoring vouchers, Johnson believes these will be helpful to inner city kids.
I give the AP credit for reporting his actual words. These make Johnson's intent clear to those who read the whole article.
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In case it isn't entirely obvious, the Democrats are owned outright by the teachers' unions - the NEA and smaller AFT. Both unions oppose school choice as detrimental to their members' interests, regardless of what benefits might accrue to the fortunate children taking advantage of school choice.