If you're arguing for relativism, you've got yourself a fine "get out of jail free" card. Every conversation can be scuttled when you play the relativism card.
If you're not a relativist, are you claiming that morals came from a deity?
If not, then... ?
Relativism in what sense?
In the sense that all values have equal merit, none are better or worse than others - no.
In the sense that morals are cultural constructs - to some extent. There are some things that all humans have in common and we have some degree of nature. We aren't a completely blank canvas. That said, this doesn't lead to any sophisticated moral code as being more objectively 'true' and it certainly doesn't lead to humanism.
I agree with most of the tenets of humanism, although from an anti-utopian perspective.
Humans are violent and history is tragic, there is no solution to this problem looking forward. A person lives virtuously in the present as it is all they can do. It is not about some mythical future, just living by your values for its own sake and with no expectation of salvation.
But you claimed that Dawkins had no evidence. I think that he does
What evidence?
Humanism in general is a big topic, so will narrow it down to this.
From the Humanist manifesto 3, that Dawkins is a signatory to.
"we aspire to this vision with the
informed conviction that humanity has the ability to progress toward its highest ideals."
What is the evidence that:
a) Humanity exists as an 'evidence based' reality?
b) We have the ability to progress, rather than progress and regress depending on environmental characteristics. That history is teleological, not cyclical?
c) informed conviction is a better phrase than "desperately need to believe, despite the evidence being overwhelmingly against us"?
And a bonus though experiment: What will happen to our 'moral progress' when overpopulation and pollution cause the ecosystem to collapse?