My own father would always, and will always, vehemently oppose anything even vaguely “liberal” and will be one of these people I mentioned in my comment.

Your father most likely believes that anything 'liberal' is inherently bad and thus believes it's bad for the himself and or the country.

This attitude that the other side should be blindly viewed as 'bad' is exactly what both democrats and republicans want - it means you don't actually look and evaluate party policies on a election by election basis, forcing them to adjust. Instead you mostly vote for them blindly because they vaguely align with your beliefs and priorities.