Along with the knowledge of programming language, every developer should have a sound knowledge of developer tools which is necessary for a more productive outcome.
Linux is the Voldemort of computers. You speak its name and everyone cowers in the corner, fearful of the pain and suffering it might bring. The thing is, Linux may have been a scary operating system before, but all of that has changed in recent years. These myths, which are more accurately called lies, are now dead.