Well we all know that the Emperors angels of death live up to their name and can mete out destruction with terrible prejudice. However, it need not always be this way when they first encounter the unknown. Although less tolerant of Xenos, there were plenty of times in the great crusade where they were rediscovering a human world outside of the reach of the IoM and had to show prowess in nuance and negotiation (certainly so from the primarchs, and to varying degrees all the way down the line).
Even in the modern setting, there are times when the Astartes have been shown to be able to speak using a language other than bolt-gun
So with that in mind, which chapter might have the most tempered approach to meeting a group of unaffiliated humans (such as the Gereon Partisans) instead of immediately decrying them as heretics and blasting them from existence? I have heard that the Ultramarines have been show to value gaurdsmen (non-enhanced humans) and treat them with better respect than other chapters, yet their inflexible adherence to doctrine might make it difficult for them to hold peaceful first meetings?
Any suggestions?
Angry marines?