There are a couple of times when one would be so angry that they may wish to throw insult to someone in a way that the said person will feel insulted. Is it even possible to insult anyone without using the swear words?
With confusion. For example suggesting that they’re an active contributor to the critical locality of dioxygenated carbon, their basic carbohydrate alkane quotient is a new record and that I simply would never have had the ideas they have.
(Critical mass of carbon dioxide = full of hot air, the most basic alkane is CH4 better known as methane and a significant byproduct of bovine fecal matter, and I wouldn’t have the ideas they had because they were too dumb to occur to me in the first place.)
One way to insult someone without swearing is by saying, ‘Are you dumb or stupid? Pick one.’ Another one would be: ‘Are you not listening, or do you not get it at all?’
When someone makes me mad enough to where I wish to insult them, I just tune them out and ignore them. I forget about them. I don't hold a grudge but I just don't allow them back into my life or my circle again.
I like to use sarcasm to insult somebody slyly if I really can't contain my feelings, but usually I can. Something like "oh my word, that's such an amazing idea, I have no idea why I didn't think of that" is vague enough to be reasonably considered to be praise, but also can be used extremely sarcastically if needed.
The alternative is to be ultra-patronising to somebody who is frustrating you. Example: "I can completely understand why you might feel that way, your feelings are valid! However, I don't agree for the following reasons, so..."
Sarcasm is a good way to insult someone without resorting to cuss words. But honestly, I'm one of those people that if I'm going to insult someone I'm going to use swear words. xD