When someone insinuates (or outright tells you) that writing isn't a legitimate career or way of life...

...ask them if they like to read the newspaper. Ask them what their favorite song is, their favorite TV show, the last movie they watched, the last book or magazine they read. The last website they browsed. The last instructional manual they used to put something together.

 Then calmly remind them that someone wrote every friggin' bit of that.