A much better question than "do rational people exist" would be "do people generally behave in a rational way?" Who cares if I'm not 100% rational all the time.

A much better question than "do rational people exist" would be "do people generally behave in a rational way?" Who cares if I'm not 100% rational all the time. As long as people in general tend towards rationality then it makes sense to talk about 'rational people.'