I can't speak for all of aikido (like some people?!) but in my experience, I have a sempai named Nashida san who trains at Shohei Juku - Takasogo dojo (in Fukuoka, Japan). He tends to work out on Thursday nights. Please go meet him and invite him to a challenge to an open-handed match. He'll seriosuly might ask you to sign some legal papers first. Go ahead. I tried my best attacks on him and he made me feel like a 2 year old. I'm not saying I'm a world class attacker, but I think you'll get the feeling that some people are more than able to modify what is done in open handed aikido to fit unpredictable fighting situations- and he'll probably not hurt you too badly unless you really are asking for it. I'm fairly certain that he has tested aikido's effectiveness out and has no interest what-so-ever to prove anything about aikido to anyone. But if you are nice and ask for a challenge I'm sure you'll get one. If you are so positive that open handed aikido does not work period, maybe you can try to wait for him after class and try to take his wallet.