>> Liberalism and pluralism do not attempt to deny other ways of life or philosophies.
> Isn’t that what you just did?
The key is understanding what I mean by "deny".
First, I'll define liberalism and pluralism as I'm using them (from Wikipedia):
> Pluralism as a political philosophy is the recognition and affirmation of diversity within a political body, which is seen to permit the peaceful coexistence of different interests, convictions, and lifestyles.
> Liberalism is a political and moral philosophy based on the rights of the individual, liberty, consent of the governed and equality before the law. Liberals espouse a wide array of views depending on their understanding of these principles, but they generally support individual rights (including civil rights and human rights), liberal democracy, secularism, rule of law, economic and political freedom, freedom of speech, freedom of the press, freedom of religion, private property and a market economy.
I'm going to abbreviate liberalism as L and pluralism as P from here on.
With this said, you can see that both L and P recognize diversity and individual freedoms to a large degree. But this is not an unfettered, unbounded, nor uncritical viewpoint. Some worldviews cannot coexist together. For example, a philosophy claiming that one group is superior and therefore may inflict suffering on others is not showing respect for the ideas of P or L.
So, it is clear that neither P nor L are compatible with authoritarian philosophies.
If you want to say "P and L deny authoritarian philosophies" I suppose that is fair enough. But I don't think deny captures what is going on very well. P and L go to great length to allow many worldviews -- hopefully to celebrate them if possible and at least tolerate them to whatever extent possible. This is quite different than dogmatic religions, many of whom claim to have absolute truth.
If you want to see a more detailed articulation of why one can accept pluralism and liberalism without resorting to moral relativism, read "Through the Moral Maze" by Robert Kane. I'd expect there are other philosophers that hold similar views. His lecture series "The Quest for Meaning" is quite good -- roughly at the level of an introductory philosophy class at the US undergraduate level, more or less.