Slate deigns to do a video on which knife to use to slice tomatoes. First, they get that simple point wrong by suggesting the second best knife, a serated knife. The best knife is a slicer, such as the Victorinox
However, that is forgiveable, as a serrated knife is indeed useful.
What is unforegivable is how she holds the tomato, by mashing her hands over it. That technique invites you to slash yourself.
The correct way to cut with a knife, as virtually anyone who actually has knife skills can tell you, is to hold the item with your finger tips, knuckles slightly bent outward, so the side of the blade is sliding on the knuckles, which means no matter what knife you use, you can nver cut yourself.
However, if you would like a demonstration of the WORST WAY TO SLICE A TOMATO, follow the below link.
WORST TEACHING VIDEO EVER