dan guthrie

I had a similar situation with someone - even newer than me - who had an "aikido doesn't work" attitude. He's a big guy and I can understand why he felt that way at first. After a few "ohmygod" lessons from a tiny Nage he stopped the attitude.
Just wait, keep training. Some of my problems took care of themselves. Remember, most of your sempai have seen dozens or hundreds of new people who stayed for one month and then disappeared forever.
I'd stay, in your case, from sheer stubbornness to prove the smirkers wrong. In my case, I'm lucky that I just love this stuff. Eighteen months and counting.