They are pretty careless and when they flip that carelessness on me (for example) becuase of my use of their vernacular in order for them to understand me as a joke, it angers me to no end.
Going back to the topic at hand, you probably could be stubborn though I can't say and you shouldn't really say that based on just being what they perceive as "negative" all the time or whatever it is that they think. Just being negative constantly doesn't make you stubborn. It's consistency, and it could just be that it's just a part of your personality. What would make you stubborn is if there was good, solid, and legit proof against your belief/case and you refused to change anyway. If you do that, then yes, you are stubborn and that's not a bad thing, though it potentially could be.
Whoever called you stubborn becuase of those reasons listed obviously doesn't know what they're trying to say.
If they are, however, calling you stubborn becuase you refuse to "lighten up" despite their wanting, then they are using it correctly. In this case, "let them suffer". It's never a bad thing to have another perspective at hand even if it's negative. This same group called the NT's usually wants you to "be true to yourself" unless of course you piss them off. Then it's a "lighten up" or whatever game then. Regardless of whatever people think, if you think you're doing fine and others say no, listen to yourself. Though that doesn't mean be naive, stupid, ignorant, etc.
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"Sometimes I've believed as many as six impossible things before breakfast."
Your neurodiverse (Aspie) score: 175 of 200
Your neurotypical (non-autistic) score: 37 of 200
You are very likely neurodiverse (Aspie)