Something I learned many years ago, in business it is never wise to put down your competition. It only makes you look petty and stupid. "If you don't have anything nice to say..."

Better would be something like this, "Pete the plumber (your competitor) is good, but here's what I can do for you..." Then upsell your strong points.

Paraphrasing from "How To Win Friends and Influence People." Dale Carnegie 1936

The problem happens when you don't have anything to upsell and the only remaining option is to try to knock your opponent thereby making yourself look bad in the process.

Unfortunately some of those listening will still cheer the stupidity.