Here, you might want to borrow this.

When they listen to Metallica.

Water you doing, bro??

Well at least you were funny about it.

They're called firefighters.

Firefighters.

Fire...fight...ers.

I'm just gonna continue repeating it until you get it because there's no simpler way to explain it.

Fire (which is a type)...and Fight (which is another type)...coming together into one word...

Fire...fighters...

Firefighters.

Get it?

The joke in the content, I get, but it seems richardastley here does not. Or do you mean he is trying to make a joke? Because feigning stupidity is not a joke, it's just irritating.

The name refers to fighting fire, as in putting it out, not fighting with fire.