But when you go from ''I want to see males that look like blank and females that look like blank'' to ''Males ought to look like blank and females ought to look like blank'' you go from having a valid opinion to being wrong and irrational . . .
I agree with this -- even if wouldn't say 'irrational' because of all the connotations of that word. I think many people have a desire to believe that there tastes are universal and natural. I suspect that this is because people want to believe their tastes are something more solid than tastes, that these are something solid, something concrete or based upon something solid and concrete.