Hacker probe/bot: AuthenticationToken exception - why?

I am developing a REST API server application. I see regular “AuthenticationToken exception”'s coming from hacker/bot probe attempts and I am irritated that Rails doesn’t check the route validity and reject the request out of hand immediately, rather than polluting my log with exceptions.

I have an aversion to seeing exceptions in the log. Is there a logic to this I am missing? What is the normal way of rejecting hacker probe bots?