Daniel lists the reasons Charlie is an asshole. Up until the Harvard debacle, Charlie had been good at absolutely everything. He's a "man's man," which, according to Daniel, means that Charlie is an asshole all of the time, and he's also ridiculously handsome. Daniel says that all of this would be fine if Charlie was nice, but Charlie is smug and a bully. To make matters worse, Charlie doesn't like Daniel.
Often, bullies are lonely or are victims of bullying themselves, which suggests that despite Charlie's popularity, he's likely very lonely. However, the fact that he got kicked out of college shows that there are major consequences for taking one's own pain out on others.