Well, dressing up like anything special as an adult is going to be viewed by some as weird. Take this adult male dressed like a my little pony horse.
Weird? normal? Any more weird than dressing up like a character and walking around WDW on halloween? My point is, it is 'weird' in that it is not the norm. Who cares tho really.
Going to WDW alone as an adult is a not the norm. Understand that some people won't get it and that is unfortunately the norm. They might even be jerks about it. Who cares. Life is short.
We had a adult (crazy?) lady on the bus last trip singing Let it Go at the top of her lungs. She had a wonderful voice so we all just rolled with it. ...keeping half an eye on her the whole time. =P. Nobody was a jerk.