I felt the 17 year old's actions were problematic enough and only through the game's plot did it contextualize why he acted the way he did so his irresponsibility made Luke unworthy of trust. He was influenced by Van anyhow so it's uncertain how things would've played out even if they did confide in him.
"It wouldn't have worked even if I had tried" is not an acceptable answer in any real situation.
Some of the characters gave him the benefit of the doubt before he went ambassador mode, which is where they started actively shunning him.
Who gave him "benefit of the doubt"? I don't really remember anything.
Ambassador Luke's callousness was amplified pretty well above what the party was used to of normal-but-acceptable in a funny way brat Luke. It was an important mission so Luke acting even more grating then usual wasn't easy to tolerate and he singlemindedly pursed his goal to the detriment of others and didn't seem to understand the suffering of others and constantly tried to pull rank in a toothless way. I don't think they were out of line, given how much Luke's (faulty) expectations clashed with the rest of the party.
They could have avoided the entire issue by simply taking him seriously for ten minutes. They absolutely did not try that. Not once. They were all wallowing in how superior they were, compared to a 17 year old kid. And they didn't blame themselves for not trying to act nicer for quite a while. Like, you know, adults should do.
Maybe it was because I was about the same age as Jade when I played the game, but my thinking was, all the way through, "how the fuck can you be such an arrogant, ignorant jerk? can't you remember what you were like twenty years ago? he's twenty years your junior, you retard" Seriously, Jade was the typical self-satisfied bad teacher type, who would rather kick a problem child out of school than try to do their job if it gets a bit too difficult.
I don't think they were out of line, given how much Luke's (faulty) expectations clashed with the rest of the party.
They didn't try to correct this. They handled him like trash from the start. Seriously, this is pretty simple. The adults had the responsibility. They (Jade especially) simply threw it away and blamed the kid, from the start. They were a complete, total failure from a pedagogical (and human) point of view. Absolute trash.