I think when a lot of trainers start focusing on speed, their form accidentally loosens a bit, increasing the chances for injury. So obviously from a safety angle, you should always strive to be tight and controlled, no matter what your speed.
From a muscle stimulation/hypertophy angle, you can create muscle stress from both sides of the speed spectrum. Going slow prolongs the time a muscle is working (T.U.T.), while going fast, or explosively, creates a higher degree of actual perceived load for the shorter duration of the movement. Both approaches have validity.
One large issue is that many newer lifters tend to come down to the bar and than attempt to explode upwards placing tremendous strain on their shoulders. When I say come down to the bar I refer to some that allow their arms to bend and go too low than when they “explode” they jolt their body so to speak creating a whiplash like affect. Stay tight from the floor so that when your body moves the bar is also moving.