The left, emboldened by recent election wins does this because they can. They seek power and one of the weapons they use against all who disagree with their ideology is bigotry cloaked in righteousness. It is fair to call them what they are: bigots.
What is “Liberal/Progressivism?
Liberalism in general is a social/political movement for change away from the predominant, existing system or culture in question to something different.