There are some very practical time-tested reasons for not dissing your competitors on a personal level.
Like it or not you share a market with this person. How are you ever going to woo away his customers by saying nasty stuff about him to people who like his product? If you waste time talking about the person, people will quickly assume your product isn’t as good as his.
Instead, try saying something like this. Paul is a hell of a nice guy, and his product is excellent, but ours works better for people like you. Hell, if it were about who’s nicer, you should buy his product because he’s much nicer than I am, and smart as a whip! But as luck would have it, our product is better for you. It has more vitamins, gets better mileage, lasts longer, smells better, gets the job done faster, for you, the most important person in the world.
Now if you make it all about how the guy who makes the other product hasn’t bathed in a month, and flunked a math test in 7th grade, well that leaves people wondering why you aren’t talking about the product.
Maybe it’ll turn out that your product is better for one thing, and theirs for another, and everyone can be happy. But dissing your competitor on a personal level makes you look like a loser.