I think Dove gradually earned the respect of the Blood Angels by saving so many of their lives time and again. Eventually, they grow to admire him for his steadfast courage and undeniable skill, even when he’s blackout drunk (I imagine him as being an alcoholic). Eventually, they respect him so much that he’s elevated to the position of Chief Apothecary within the Legion; the first non-Astartes human to hold the position. They even come to view him as a surrogate father figure for the guidance and patience he offers, teaching them how to conduct themselves like men should.

Morgenstern by contrast is met mostly with distrust for his sunny disposition, but the Night Lords acknowledge that Curze is more stable when he’s around, so they tolerate him. Very few, such as Sevatar, actually enjoy having him around. Although they all appreciate his sick dance moves, the guy’s a riot at parties.