For the left, politics has replaced both religion and philosophy. It can be seen in their ever changing and logically conflicting positions in a whole range of issues, their conflation of moral positions with political ones, their refusal to see or allow to be seen anything that contradicts their beliefs, and even in their friendships. Yes, even personal friendships are impossible outside their faith. It isn't just a religion, it's a rabid fundamentalist religion.
What is at the heart of a liberal society? It is to uphold that we have a right to offend and a duty to tolerate offence. George Orwell said: “If liberty means anything at all, it means the right to tell people what they do not want to hear.”
In discarding Christianity, we kick away the foundations of liberalism and democracy and so we cannot then be surprised when what we call liberalism stops being liberal.
My experience is that although liberalism has won, it is now behaving like the established church of the empire in the fourth and fifth centuries. It has gained ascendancy and lost itself in the process. It isn’t very liberal any more.