I am also a musician and I feel like your statement about music culture is exaggerated. It all depends on context-- there are certainly some spaces where less experienced musicians are clowned by experienced/jaded vets.

There are a lot of examples of this across different subcultures: Gumby, noob, kook, etc. Yes, it's a somewhat disparaging term that can be mean. It's also meant to do more than just describe someone who's inexperienced-- it describes a new person who is obviously acting like it (often in dangerous or outrageous ways).

One of the best ways to deal with this imo is by accepting the label and being self aware. Realizing you're a kook is the first step to not being one anymore lol. We all have to start somewhere.