It is very rare that anything remains an undeniable fact for too long, especially when you consider people's views and differently acquired knowledge. We are in a constant state of change. We think differently as we gain knowledge and skills in thinking. One generation to the next have different aims, ambitions and morals. What might be seen as a good thing by one generation could be seen as a bad thing by the next.
Political parties change their views, as do their voters.
Due to personal circumstances, individuals can change their whole philosophy of life within months. Technology and other inventions now change the world faster than most people can keep up with. What seemed impossible one week can become plausible the next, reality within months and an accepted way of life in a year or two. This is not really surprising when you consider the combined, diverse thought power of billions of people spread across the globe. The way to answer these questions is to challenge the facts.