Well it turns out that there is a good reason for this. While psychologists think it stems from their transgressive behaviour (unpredictable and antisocial), neurobiology has a different take and is much deeper.
Exaggerated facial features pushes the clown into the “uncanny valley”.
This phenomenon was identified by Masahiro Mori ( a robotics professor ) in 1970 and is used to describe the feeling people get when something appears not quite human.
So people are quite happy with robots that look human or look distinctly not human, but get distinctly uncomfortable when they look nearly human. If you plot this on a graph there is a steep drop off at some point, hence the “valley”.
Thanks to Dr Max Pemberton’s column for reminding me of this interesting fact.
Check out Wikipedia for more info.