Should People Without Kids Stop Giving Parenting Advice?

Was talking to a friend of mine the other day and they told me a story about a friend of theirs that knows everything. They were talking about how to appropriately discipline my friends 8-year-old, which led to a huge argument.

The kicker was that this guy doesn't have kids. He does not work in a profession that would give him insight on how to handle parenting.

I'll admit, sometimes parents are overly sensitive when it comes to how they handle their kids. Whether they are right or wrong they will be combative if criticized.

Should people without kids be giving advice on how to take care of kids?