Dislike for James

pHi! First-time Poster here, so please be gentle. I re-read Gatsby recently, and am left slightly confused. The nature of my ponderance is as follows:

Why does Nick initially dislike James? For that matter, why do many of James' guests harbor an unspoken disdain for him? Is it purely because Gatsby is nouveau riche? If the dislike surrounds his business dealings, would James' cavalier, mysterious operations be something to admire, and not scorn, a la Bonnie & Clyde?

Nick failed to muster funeral attendees. Was this purely because people never liked James, and his nefarious business dealings? Or, did they believe he cruelly slaughtered Myrtle? The court case was after the funeral. What insult did the neighborhood children inscribe on the bricks, that Nick defensively removed with his shoe? Why would kids dislike Gatsby?

Old Sport: did James learn how to talk rich from Tom? Brushing aside readings interpreting homosexuality into their relationship, did Gatsby assume Tom's personality in order to fulfill his quest for Daisy?

What is the significance of James' pink suit?

Thanks in advance for any insight you can share.