It's always the people who know the least about a given topic that seem to act like they know the most.
The only people I've had give me grief over a 250 are my nieces' boyfriends, one of whom is 16 and has only had his license about 8 months, the other being 18 and has done pretty much nothing except school and football.
The younger one teased me and said "I thought you got a sport bike, all I saw was that girl's bike out there." I just replied back, "Hmph.. I didn't see your Hayabusa out there, where's it parked? I want to take a look at it." He just looked at me for a second and asked "what's that?" I just said "exactly" and walked away with a grin.
The other boyfriend said pretty much the same thing, amid a conversation between me, him, and 3 other people: "so how do you like your chick bike?" Trying to be polite, I just said "asphalt doesn't care how fast my bike can go when I'm sliding on it at 70mph... my 'chick bike' gets me around just fine. I don't think I'd be around very long if I started on anything much bigger." Later on in that conversation he tried to get a dig back in on me about not having enough power to get out of its own way, to which I again replied "I forgot, what bike do you ride again.. how long have you been on it?" Everyone else basically understood it as me telling him to STFU and laughed at him. Oddly enough, he walked off after that.
I have a much older cousin who rides a Harley - have no idea what kind - and my first group ride was with him, my dad, and his friends who all had Harleys, they were the typical leather vest, melon-catcher helmet HD riders and even THEY didn't give me crap over my Ninja 250. They just all agreed "yea, it'll be fun for you this summer and then maybe next year you sell it and move on to something bigger." I won't say I can't disagree about wanting to move up to a 600 or something in a few years, but not anytime soon.