I think you are failing to take into account that friends and family play a big role in the judgments that every individual makes just as much as our own experiences. Maturity has little to do with making your own judgments. One's own judgments can be equally mature or immature. It's all based on the individual, their experiences, and the family and friends around them. I would say if my best friend is telling me, "You know I really can't stand that guy. He's a bit of a douche bag", I'm more than likely going to take my friends word on it, not because I am immature or lack any of my own opinions but because I trust my best friend. The same goes for family as well. These people know me and know how I am as a person, so if they are telling me to stay away, I likely will.
This doesn't mean that Love hates Lebron because Rose does because I don't think Rose actually hates Lebron. He's just not his type of guy. Rose is quiet and introverted. Lebron is loud and obnoxious a lot of the time. Those types of people just don't mix. On the court, I'm sure they could be amazing together, but that doesn't mean that have to all be best friends off of it. This whole buddy-buddy AAU culture that has permeated the NBA is slowly destroying the competitive nature that I absolutely loved when I was growing up.