It's also possible that Chen doesn't know how emails work and just assumed it was sent. My uncle thought that deleting shortcuts from the desktop = uninstalling programs.
As a fellow CA, I can relate to your situation. I just want to remind you of some racism and sexism that can exist - for example, Kyle being white and an engineer (with a job/internship) is different from a minority engineer (with a job/internship).
Chinese culture is definitely less formal about things like this, so when Chen asked your bf about a job, he probably had completely different expectations (this is especially true if he lives outside of China/Chinese territories and hasn't assimilated but lives in Chinatowns and Chinese communities). Now that you guys are running into problems, he sees this as a change in terms- that your boyfriend (notice he didn't ask you, I don't know if that's a sexism thing man-to-man and whatnot) reneged on his promise. He might not understand the awkwardness of the situation - or if he did, he saw a good opportunity to corner your boyfriend into agreeing.
A part of Chen's rage may come from saving face - he probably already bragged about having connections and now fears he looks like an idiot. This has happened to me so many times that I find it too painful to even get popcorn and watch the adults in my family lose their heads.
I also have a related anecdote about family asking for favors. For years, whenever I went to visit my relatives, everyone would always ask me to fix their computers or shit like that. It was really annoying to go in expecting to celebrate someone's birthday and having people corner you and pester you into doing things without even so much as a thank you.
On top of this, my relatives were all from China, so they grew up in a different culture where blunt, degrading comments to a growing child were not seen as bullying tactics. Their approach became slightly less severe when I stopped visiting but their mindset is still the same. Their kids do not respect boundaries and they have argued among themselves over perceived slights and disobedience.