I agree, if someone can play, then they'll get respect. In most cases, a nasty attitude could be others just misjudging him and misunderstanding that particular person as many people do.
Respect talent and give someone the benefit of the doubt when it comes to a bad attitude. Everyone has a story that we may not know...but they had enough discipline to master their craft and I'd respect that any day.
i think there's a difference between the reception of such people with other musicians and non-musicians. with non musicians, if he walks in with a keyboard, assumptions are that he plays keyboard and automatically that means he's in charge of the music. ive been learning keys, but primarily a bass player, and ask any of my fellow bass players and drummers how many times we've been there, with no organist/keyboardist and folks say "we're waiting on the musician to show up". or you could have an 8 year old on keys that just started learning 2 weeks ago and have other musicians that been playing for like 30 years on the pro circuit, and everybody lookin at the 8 year old to say whats what just because he's on keys. so in that case, with non-musicians, yes i think you get instant reverence.
with other musicians however, you have to prove yourself. everybody is gonna want to see what you have to offer, particularly if ur a "nobody". Your attitude is key to how you are received. If you are humble, people will see your skill openly. If you arent that skilled you'll have people willing to help you out, encourage, give you pointers, invite you to jams/shows/rehearsals to come watch and learn, etc. If you're skilled people will look to you for those things. Of course you'll have the haters in either scenario. But if you're all cocky and full of yourself, nobody really wants to deal with you anyway. A big problem with some, is that they go the humble route UNTIL they establish themselves, then they become arrogant and such because they know they're skilled.
Be careful with the expensive equipment; the more exotic ur equipment, the higher the expectation of you is. thats just the reality of things. same concept goes with any aspect of life. I started out with a $150 yamaha ES313 and then upgraded to a Yamaha MM6 which i love. This is even worse in the bass and guitar realm because theres so many more options and then u delve into the custom made items as well. I say when you go out, bring something that best reflects your skill level. If top of the line/bottom of the line is all you have, then put your humble attitude on overdrive.