So how true is this?

Not very true as far as I’m concerned....I’ve been a moderate most of my life (more conservative with regard to economic issues and more liberal with regard to social issues).

I have a heart and a brain (that I didn’t need to get from The Wizard), but don’t consider myself liberal or conservative....and, if anything, I’ve become slightly more liberal with age.

It’s pretty much a throw-away line based on some people’s experience. It might be true for some, but it’s far from universal.

🎶 Label me I'll label you...

I don't find that to be true

If you are in your twenties and not a liberal, you have no heart (or more like you need to do some more developing). If you're in your thirties and a conservative, you have no heart.

The statement isn't true, it's just a pithy-sounding meme and of course conservatives like it.

Defining people by a single word is rubbish.

No saying can always be true the same way the saying isn’t always wrong.