As others have said, when people already have their minds made up regardless of facts, it's next to impossible to change their minds. You might try to make them back up what they say, they probably won't (and can't). You can show them your code and how readable it is, they'll probably still blow it off ... sigh.
I'm working at a job in perl and like most of it, at least far as the perl stuff goes. I was told that a few years back they had trouble finding enough good perl programmers and decided to switch to PHP for the next version of our product (it's web based SaaS). But we'll still be using perl for the next 10 years or more because we have a lot of older clients who still bring in a lot of money for us and some of them like the older software better than the newer PHP software, because the perl software runs faster.
Don't give up hope. You may have to find a different job if you really can't stand it. As painful as it is to change jobs, you'll be better off if you really dislike your present job that much.