Because when used in politics the words 'liberal' and 'conservative' are merely names and not necessarily philosophies. Yes, decades ago the American Democrats were the conservatives and the Republicans were the liberals, but times change. Going back to the founding of America it can't be denied that the Constitution was a very progressive document for its time, as were many of the 'founding fathers'. As a measure of how quickly things change, by comparison to the current Republicans Barry Goldwater would be considered a flaming liberal.