When this dialog happens? At the first time, or after conversation with barbarian Cheiftain?

It should be after the first chieftain meeting where the chieftain has banished your guide to an island where the dead.

It all depends on who is the 1st party member, as well as the wisdom, intellect or charisma stat and possibly the class that has the best chance to talk without fighting.

My blade who was first in party was able to parley with Angaar without a fight

I had to put my Skald in the first spot. I think you need intellect to get the dialog option and rizz to pass it.

full spoiler for this place, tldr - charisma 14

Once you're back outside, Angaar tells
you that he was ordered to kill you. Ask about Hjollder for some
experience, and avoid a fight for yet more experience (you'll need a
Charisma score of 14 or higher to pull this off-again, Friends will do
the trick). Well, that leaves us with one thing to do, I guess. Time to
head for this cheerily-named Burial Isle. Talk to Angaar again and ask
him some questions to get more information out of him. Note that as a
party we've gained a total of 416,000 experience, or 69,000~ experience
per member without doing a bit of fighting. It seems that-despite the
warning at the beginning of the expansion-the designers wanted to buff
your party up before throwing anything at you. Still not enough, you
say? Very well.

Source: https://gamefaqs.gamespot.com/pc/871349-icewind-dale-enhanced-edition/faqs/70660

I dual classed a fighter to mage and the Baldemar convo got him to 7.