There are also developers who view Java as the one true programming language who are either unwilling or unable to learn anything else. I know they exist because I've worked with many over the years. Javascript seems to be accumulating people of a similar mindset these days as well.

Filtering these clowns out should be rather simple (make sure their resume mentions at least a few different languages and ask the right questions during a phone screen), but most companies aren't willing to expend the effort.