Not true. I used a sight pusher on my G19.If you are asking about a Glock, I can assure you ANY night sights have been installed with a mallet. It takes them about 15-20 seconds per pistol.
If you plan on ever replacing sights on pistols you purchase in the future or to upgrades signts on guns you already have, I cannot recommend highly enough getting a sight pusher. They are really the "correct" way to install sights and I think offer much more minute adjustments.
I have this one as well. Can't beat it for the price.I use a sight pusher. Nothing fancy, just makes it easy to do small adjustments and swaps.
Standard Handgun Sight Tool | Sight Pusher
sightpusher.com