One of the phrases most guaranteed to annoy usage traditionalists and purists is beg the question meaning raise the question or evade the question. While raise the question (or invite, elicit, prompt, etc.) is by far the most common meaning, it differs from the initial philosophical one. So it makes a good case study for language change and attitudes to it.
First, the traditional use: beg the question was originally a logical fallacy also known as petitio principii. It’s kin to circular reasoning in which a person assumes the conclusion in their premise. That is, the truth of their argument is based on an assumption that hasn’t been proved, and needs to be.
Same-sex marriage should be forbidden, because marriage must be between a man and a woman.
Democracy is the best system of government because of the wisdom of the crowd.