How to Tell Someone Off Without Sounding Like a Bitch. Help!

I'm single and looking! If you guys haven't noticed I'm looking for a playmate between the ages of 18-26, male or female. I mean I am 22 and I don't think I sound crazy in wanting a man or woman close to my age. One of the main reasons I decided to do this was because I kept getting gross emails on TMF from 40+ males. I just feel that a man or woman close to my age will be able to love me for who I am. I feel most of the older people are dirty, desperate, and just want to tap a 20 year old. This thought just creeps me out. Unless the older man looks like Johnny Depp and the girl Michelle Pfeiffer, I wouldn't even consider trying to hooking up with them and I still would want to be sure they want me for me not because I'm a hot youngin in their eyes. I recently joined FetLife and decided to put the same age limit on my about me.So far so good, but a guy just sent me an email wanting to become my playmate and he is 31. I know that even though I ask for a certain age limit dirty older people will try to hit on me. My question is how to I put them of gently and polity? I've always been bad at this and I usually just ignore them, but I always feel rude when I do that.I don't want to be known as a bitch.😕