Telling your readers that something goes without saying or something should go without saying and then saying whatever it is, is almost like telling your readers they’re too stupid to know that something should go without saying. Do you get what I’m saying? It’s insulting to your readers.
This is one of those phrases that people use to highlight what they’re going to say next, to make people sit up and pay attention. It’s also one of those phrases that we subconsciously pick up and start using in our own writing and conversation.
But the big problem is – it’s also one of those phrases that you don’t really listen to. If you did pay attention to it, like a lot of Grammar Nazis do, then you’d realize that it’s really kind of offensive. It makes you look arrogant, which turns people off.
If it should go without saying, then don’t say it. But if you think your readers really need to hear it, then don’t tell them how ignorant they are for not knowing it in the first place.